Unfortunately, as much as I hate to admit it as someone who has left Chromium behind personally, Chromium is kind of the only choice. I think people outside the browser implementation world underestimate the sheer scale and complexity of the modern browser stack and what goes into maintaining compatibility with web standards, much less advancing them.
We’ve reached the point where Chromium is essentially the de-facto web standard because Chromium engineers do the lions’ share of feature testing and development, because Chromium receives the lions’ share of funding.
Igalia, an OSS consultancy that does a lot of fairly-funded independent browser development, has lots of material about this. For example, the recent chat between Igalia members and someone from Open Web Advocacy about what to do if the anitrust ruling against Google jeopardize’s Chromium’s funding, and the options are pretty dire.
Edit: After reading the article, I think this is a really good sign. Bringing together the immediate stakeholders in Chromium’s development and funding bodes well for the possibility of stewarding Chromium in a less Google-dependent, profit-motivated, ad-centric direction. There’s unfortunately a lot of uncertainty about how this will all shake out, but it’s possible that Chromium could become a truly independent project and move back in the direction of user value instead of user-hostile shareholder value.
I think anyone is welcome to try this, but the core ethos of the web is backwards compatibility. To my unending irritation, even non-standard behaviors/APIs like WebUSB have become critical for sites to function.
The last time we actually dropped a feature, it was Flash, and that took a decade and there is still tons of effectively dead/permanently lost content because of it.
Creating a browser that only implements a subset of the standards is fine for very niche usecases but I don’t expect it to ever overtake the major browsers. We’ll see how Ladybird fares as it’s compatibility increases.