Hey Starborn! Welcome to the Pokecommunity!
Ooh so you were a speedrunner back in the day? What game was it, and what made you stop? To answer your question, honestly not much changed what with how the game's played lol. That can be either good or bad depending on how you look at it. It's still the same concept of become the strongest trainer of your region by mashing attacks at whatever Trainer you lock eyes with.
One thing's for sure though, it ain't as popular as it used to be. I guess it just became too formulaic for a lotta people and the new designs didn't appeal to everyone. There was at least that big spike around 2016 with GO, but that's died down too (also didn't it mostly just feature older gen pokemon anyway?). Nowadays I guess it's mostly stabilized and we're left with either the ultra casuals or the ultra die-hards.
I lean more towards the casual side of things (so I can never dream of speed running games like you lol), and focus more on the community contributions. Namely, romhacks. Ugh the quality of those have skyrocketed in the last few years and it's been such a fresh reintroduction for me to the franchise. If Game Freak can't pull the weight, the fans will.
Anyway sorry for the life story. Hope to see you around the forums! Have a great day :D