As long as we’re filling out our fantasy browser brackets, I’m hoping that the Servo engine and browser/s can become viable. Servo was started at Mozilla as a web rendering engine only, before they laid off the whole team and the Linux Foundation took over the project. Basically revived from the dead in 2023, the current project is working on an engine and a demonstration browser that uses it. It’s years away from being a usable replacement for current browsers and the engine is certainly the main project. A separate browser which employs Servo as its engine is a more likely future than an actual Servo browser.
Still, you can download a demo build of the official browser from the web site. Currently, it’s only usable for very simple web sites. Even Lemmy/Mbin display is a little broken, and I think of those as fairly basic. YouTube is out of the question. One of the sites that’s been used to demonstrate its capability to render web pages is the web site for Space Jam (1996) if that gives you any idea of its current state.
Adding on to this, while this article is fast approaching 20 years old, it gets into the quagmire that is web standards and how ~10 (now ~30) years of untrained amateurs (and/or professionals) doing their own interpretations of what the web standards mean–plus another decade or so before that in which there were no standards–has led to a situation of browsers needing to gracefully handle millions of contradictory instructions coming from different authors’ web sites.
Here’s a bonus: the W3C standards page. Try scrolling down it.