In theory it can, but when you work with 20 other devs all working on the same codebase, tracking those changes can become burdensome.
Are we going to add an entirely new testing suite and workflow tools to save 5 lines of legacy CSS in favor of the new version? Probably not in a lot of teams.
You also need to write and maintain code to conditionally load that fallback stylesheet and hope your users aren't using some weird user agent hacks (looking at you instagram in-app browser).
All of these problems can be solved, but obviously nobody wants to because the juice is not worth the squeeze. This is not our first rodeo. I'm gonna wait another 18-24 months and then start using most of the features released this year. It's fine.
Are we going to add an entirely new testing suite and workflow tools to save 5 lines of legacy CSS in favor of the new version? Probably not in a lot of teams.
You also need to write and maintain code to conditionally load that fallback stylesheet and hope your users aren't using some weird user agent hacks (looking at you instagram in-app browser).
All of these problems can be solved, but obviously nobody wants to because the juice is not worth the squeeze. This is not our first rodeo. I'm gonna wait another 18-24 months and then start using most of the features released this year. It's fine.