We could have kept that creative environment (that seem to just disappear without any alternative to this day) while leaving videos to evolve as they did.

People here complain like they have issues with long term memory, but reality was - there was no real web video before. That apple had more issues than others was problem that should have been contained to apple walled garden alone. World was, is and will be much larger than that.

That 'creative environment' was mostly used for obnoxious advertising by the time flash died.

The creative environment could have been built with HTML/JS as well. I feel what killed it more so was mobile gaming took over casual games, and modern game engines enabled a single person who would have been making dinky little flash games to now make what used to take an entire studio.

Maybe, but playing videos was 99% of the use case for Flash by the time it was killed by Apple. Adobe could have kept maintaining it for the 1% Flash games, ads and terrible websites, but you can see why they gave up...