Accessibile UIs are possible outside the browser as well. Lots of native applications exist that are accessible by e.g. blind people. Actually a lot of that stu

Accessibile UIs are possible outside the browser as well. Lots of native applications exist that are accessible by e.g. blind people. Actually a lot of that stuff existed before the web was even a thing. All that stuff can now be compiled to run in a browser. The majority will continue to follow the easiest path. Which is not necessarily JS+DOM+CSS anymore. And contrary to your point, there always was a lot of friction with flash and Java or other plugins like silverlight. You had to install them, you had to keep them updated, they had security and performance issues, etc. General design by committee browser standards are kind of very limiting however. It doesn't even come close to what was possible 15 years ago with flash and shockwave. That's why games don't have browser based UIs for example. They suck. It's just not good enough if you are trying to immerse the user in a futuristic and playful game world. That's also why mobile phones have native UIs. We can do better than dom+css. Way better. And now that we no longer have to stick to just ccs+dom in a browser, inevitably people are going to make use of that.