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.