A lot of the optimizations are not some ground breaking new way to program

Hindsight is a bitch huh? Everything looks simple now once people proved it kind of works, but I think you over-simplify "how easy it is".

Lots of stuff in ML, particularly recent ~5 years or so, haven't been "implementing old algorithms" although of course everything is based on the research that happened in the past, we're standing on the shoulders of giants and all that.