Alexa (and the google equivalent) were an over-exuberant experiment. Speech is an interaction mode, not an all-encompassing one, and also a low-bandwidth one, so a device centered on it can't ever be a general computing device. Amazon tried to think a bit more broadly by having other on-keybaord interaction modes (buttons, which were really just clutter because their use was infrequent, and their wand, which was actually pretty handy) but again, didn't integrate it deeply into the rest of their world, so died due to lack of imagination.

Google's thing is even more stark because it had no primary raison d'etre so I only ever saw one in the wild and it was at a google employee's home!

Apple went the other way, making a speaker that you could also talk to. Of course Siri is such crap that it's fundamentally "un-sirious" too.

But speech is not a terrible adjunct. I often use speech to control my watch (start a workout, set a timer, what's the weather outside) bc the screen is so tiny and the controls so few. It sometimes tells me things if I am wearing airpods. But I have the watch cranked down to only provide me with a few things, mostly by glancing at it after it taps me. And who would design a tap-only interface?