Endorsement by browser makers is not enough, because browsers are far from the only software that uses the internet. We would need to rewrite every single one of these software to successfully make the transition. In an ideal world where legacy software don't exist and people would rewrite their software to adjust to new standards overnight, yes it might work but that's just not the way things are. Worse, things would break badly when we have different software using conflicting naming systems. I'm pretty sure nobody would want to spend time debugging that kind of mess.

Now, even if browser support is all we need (it's not), how can we possibly explain this to users? Many, many links, bookmarks, and URLs would break along the way, causing confusion and harm.