Knowing several autistic players for whom absolutely none of that is applicable, I'd say you had bad players. The "self-described autistic" element doesn't have much to do with that.

Not everyone who wants to do a thing can or should do the thing.

It sounds like you just had some awful players, I've played with a lot of people on the spectrum and the majority of the time they've been fine to play with

I’ve had similarly poor experiences, unfortunately. I have two autistic friends, and they’re good people, but they both have very… specific ideas of what a fantasy world must entail, one of which is far more attainable than the other, if they could properly play along. So one wished to be a mary sue-esque elven princess wizard, which I okayed because they were at least trying, although decisions such as weapons, prepared spells, and especially combat were harder for them so I guided most of those. My other autistic friend was particularly difficult though. His favorite character is from a retro video game, and he wanted to play that character, which by itself is fine. However, he wanted to play his fanfiction version, which he said was a “lone wolf” who wouldn’t stick with the party, and he wanted his uber-special one-shot sword. I worked to bring him down a peg and got him to agree that, for the sake of the mission, he should stay with the party and if “lone wolf” is particularly important we can do games outside of the main ones too. Unfortunately that session ended rather poorly because not one of my 5 players could focus.

The last session I tried a year or so ago, and had the same person fanfic-writer attempting to demand control for everyone in the party because he “was the better tactician” because he “played Fire Emblem before”. My players ignored him and he got upset, and I had another player leave for unrelated reasons (D&D just wasn’t their thing, which I understood).

Now he’s been “trying” to make his own campaign, so he can get the control he desires from running the monsters, but that’s been somehow slower than his other projects.

Typing this out made me sad too, I haven’t been able to DM properly for a while.

Those are not autism problems. Those are indeed, self-described and they’ll find any currently popular excuse to clear them of any responsibilities

self-described autistic players

I am going to say the terribly unfashionable, nay almost heretical for today's climate.

I am fairly convinced vast majority of self-described medical conditions, are not. I believe they are "trendy diagnosis" or "fad syndrome".

Certain medical conditions receive heightened attention in media, leading to increased self-diagnosis or people claiming to have the condition because it's seen as socially or culturally relevant.

Anyone recall the rash of Tourette syndrome TikTokers after an individual with the syndrome posted a highly viewed clip?

e.g., ADHD, Gluten Sensitivity, Chronic Lyme Disease, Fibromyalgia, Multiple Chemical Sensitivity (MCS), and Autism or Asperger’s Syndrome.

I'm sure it is all more pronounced with someone who is truly deep enough in the autistic gamut, but for each of those complaints I can name at least one person in my life who, while not on the spectrum at all as far as I know, exhibit that trait. Particularly the time keeping and communications ones, I could name several for those. Myself certainly on timekeeping (though I do at least let people know my estimated delay!).

Would highly recommend checking out Critical Core - https://gametogrow.org/criticalcore/ which makes it much easier for both players to start and DMs to manage

If you are running a pickup game open to new players you will probably have all the above problems which is part of the reason why I'd never run a D&D game.

If I were going to run a game it would be a second-generation or later game like Toon or Paranoia or Call of Cthulhu which were all designed by people who played D&D and recognized what was wrong with D&D and the culture around it.

To be fair newer versions of the game fix some of the brokenness such as too many kinds of dice (you think it is fun until you realize that unless you buy 20x as many dice as you need you're going to always be looking around on the floor the right dice, and there's nothing dramatic about rolling 20d6 for a dragon's attack because it's always going to do about 60 points of damage, etc.)

Second-generation games give you everything you need to start in a single book (even a scenario) whereas with D&D you need to buy several books just to get started.

The long-term character progression works OK in a group of committed players but it makes the stakes so high that players take it so seriously so it is not a lot of fun for the DM. In a shorter, simpler game with higher character mortality you can give the guy who came in 30-40 min late a preroll, a minute of instruction, and some pretense for why they are late and it's NP.

I am not going to say it is the high point of DMing because it isn't but if I want to run a Paranoia game in a hurry I can kill off most of their clones before they get to the briefing room in my very dangerous Alpha complex with little-more-than random encounters and have them rolling on the floor laughing and coming back for more. Prerolls are probably more important preparation than an actual scenario because if people aren't fluent with character creation they're going to ruin it for each other (e.g. if you are creating new characters you want to have 1-1 sessions with players and not do it in a group... In D&D in particular you could spend years with a character and there is no way you want to rush the process, if I really wanted to do a D&D activity with young people I might just have them do nothing but create characters so they can get fluent)

Unfortunately the same way that "autism" and pill-seeking behavior have crowded out awareness of other neurodivergences, developmental disabilities and mental health conditions, D&D has crowded out awareness of other tabletop RPG's so you will never see some study where people find 5 out of 75 depressed people had fun playing D&D and 62 out of 75 depressed people had fun playing Toon.

My experience with people on the spectrum (I'm a card carrying member myself) is very diverse but there is a constant: they're stubborn on specific stuff where others are not. For example, I don't want to sit near someone who's eating hard cheese (non-melted). I don't mind someone eating whatever though (and even if I would, personal choice). Looking back in my life, I learned a lot from RPGs (Hero Quest, Star Quest, various Gameboy Classic games, Warhammer Quest, Warcraft franchise (story-wise, too). More so than RTS or FPS. But I have also been nigh annoying whilst playing them. It helps to learn you are being annoying, as conflict allows one to rise up to the occasion. That being said, you need to accept certain quirks as being part of the package. That is how any friendship or relation works; just people with autism are usually more accentuated. My wife and I are both on the spectrum, and we need to work with/around each other's quirks. Just the other day she demanded me to clean and refill a water bottle as she tastes other people otherwise. She even has that w/me, I found out (we are together for almost a decade). So I ended up cleaning it (she was with our son who was ill).

Bullets don't work in HN markdown.

Constantly having to remind them of rules from session 0, such as 'no alcohol before or during the game'

That sounds like the most boring DnD session ever, we get so high that any underlying condition is masked by having a damn good time. ;)

Being unable to complete a character sheet unless someone walked them through it and made every decision for them

We used to play various table-top role-playing games over 20 years ago. D&D is known for its totally humiliatingly complex character creation, which is usually totally unnecessary, especially when ‘learning’ new players.

Edit: sorry for my confused mind; I meant DSA not D&D.

Character background is also not that important in my opinion. You simply explain that the goal is to play a role and that the character's background is important and determines his actions. Demanding that everything is well thought out increases the barrier to entry immensely. So keep it simple.

I remember my first ~~D&D~~ (Edit: DSA) sessions with new groups where it literally took us 5 hours to get all the characters ready.

Our group, after years of experience, simply explained the world to new players (we preferred to play World of Darkness, or shadowrun). We asked them what they wanted to play and roughly decided together with them what their strengths and weaknesses were. Rolling dice was more of a show for the newcomers, we hardly ever rolled dice ourselves. If you had 9/10 points in physical strength, we didn't think you needed to roll if you hit someone in the face. That just hurt.

Our rounds became more and more enjoyable over time. Fewer rules, fewer dice orgies. More common sense. More focussed on each other and on the game itself. At the very end, we even played without a game master. Often ancestor rounds in world of darkness (vampires that were several hundred years old. Something like demigods.) Dice rolling was more or less obsolete. We had night-long in-charachter conversations.

Oh, I miss that very much.

I have autistic traits and it definitely helped me to put myself in other people's shoes. But it helped me even more to overcome my speech disorder and to learn how to deal with it (stuttering).