I mean, if you can easily update whatever userland library you're using, why can't you upgrade your OS? If the library is easy to upgrade it means that it uses a well defined and backward-compatible interface. What do you get by shifting everything one layer up? In the end it's just software, there's not really any reason why upgrading a kernel driver should be any harder than upgrading a .so/.dll.
So the logic is "kernels are too slow to update and integrate the last new standards, so let's just move everything one step up because browsers auto-update"? Except that there's no technical reason for that, on my Linux box my browser and my kernel are updated at the same time when I run "apt-get upgrade" or "pacman -Syu" or whatever applies. The kernel I'm using at the moment has been built less than a week ago.
So if the problem is that Windows sucks balls and as a result people end up effectively re-creating an operating system on top of it to work around that, then yeah, from a practical standpoint I get it but I'm definitely not "_very_ excited" about it. It's a rather ugly hack.
If in general if the question is "who do you trust more to select and implement new internet standards, kernel developers or web developers?" then I take a side-glance at the few GBs used by my web browser to display a handful of static pages at the moment and I know the answer as far as I'm concerned...
So yeah, it might make sense, but I still think it just goes to show what a shitshow modern software development has become. Instead of fixing things we just add a new layer on top and we rationalize that it's better that way.