It's not that hard to build a browser (I'll say this because I've done it, and there are plenty of people who have done it better.) It's just tedious and not something you can put on the app store.
One that reliably runs all the javascript needed to support modern Twitter/Facebook/GMail/whatever style webapps? I mean _maybe_, if you're pulling in someone else's code as dependencies to deal with your javascript runtime and your rendering engine. A lot of people could hammer out lynx or w3m in a weekend, but not something that'll run Twitter. (Hell, the Safari Tech Preview occasionally chokes on Titter...)
There were simple technologies which did a lot too, like Hypercard.
The creeping complexity of the web isn't something which had to happen. I understand the reasons it did happen, but in an alternative timeline, without Netscape vs. IE, the dot-com boom/bust, and the whole Netscape meltdown, it might not have happened.
People were building sophisticated applications which did a lot in the days of NeXTStep, BeOS, SGI, and Amiga, without this massive complexity build-up. Altavista scaled well too.
That can stay within the browser or some shared library. It absolutely doesn't need to affect unix/linux architecture in any way.
[1]: https://drewdevault.com/2020/03/18/Reckless-limitless-scope....