Building a web browser is a difficult, but attainable task. On the other hand, getting the UX right is a gargantuan task that even big tech struggle with.
Actually, UX is much easier to iterate on. There are countless Chomium implementations that are mainly competing on UX. They all render websites just fine. UX is the only thing they compete on. Mostly, there is a lot of imitation and not a lot of innovation in that space. It seems people like tabs at this point and things like bookmarks and back buttons. There are only so many ways to arrange those features on a screen and we've seen most of those over the past 20 years.
The real difficulty with browsers is building a better one than the existing ones. If you make a new browser. It does exactly the same thing as the other ones. It's a great technical accomplishment but it has a very low value. Which is why nobody bothers at this point.
At this point there are only three browser engines with any audience still worth talking about: chromium, safari/webkit, and firefox/gecko. Obviously the first two are related but they forked so long ago that they are quite different at this point. In terms of what they do there are some minor differences but they basically render the same websites in more or less the same ways. There is very little point in picking one over the other at this point.
I actually use Firefox and I'm pretty happy with it. I don't think it does a lot better/different than the other two at this point but I like not selling out completely to Apple/Google. Google treats me like a product rather than a user and Apple seems more interested in telling me what I can't do rather than enabling me to do things I want to do. But objectively, both do a fine job of rendering websites and allowing me to browse the web. Just like Firefox does. And given that there is no practical difference, I choose to use Firefox.
