What makes you say this? Just because someone used AI to port some classic productions to the browser (which is actually pretty cool), doesn't mean that AI has taken over.

AI slop productions tend to be frowned upon, or even banned, writing code and using cool tricks to to what seems impossible is still a big part of the demoscene, in particular in the sizecoding, oldschool and wild categories. Clever use of AI is a debated topic, the demoscene is about pushing the limits of current technology, and AI is part of current technology. There is also the question of using AI for tooling (modelers, compressors, test harnesses, etc...), as in, will you stop using a particular IDE because it is written with the help of AI, even if it is good?

But still, most productions are hand made.