SerenityOS Browser now passes the Acid3 test (https://news.ycombinator.com/item?id=30853392)
That is a new browser from scratch, (well actually, it is a full OS from scratch). I got the impression this is developed by very few persons.
So to answer your rhetorical questions:
Q: who could?
A: Andreas Kling, Linus Groh and Sam Atkins
Q: why?
A: Because they want to use it. "This is a system by us, for us, based on the things we like."
In a few years when they have achieved feature parity with Chromium or at least Safari we can discuss this again, but for now it's not ready for real life use.
The lone effort of a handful of developers that got equally far is worthy of a mention as a "new browser" even if it's not fit for human consumption yet.
So until then, why moan about the things people are doing to innovate in the space even though they’re using an off the shelf core.
Mozilla.. basically they're lingering on due to Google's fear of having the only browser available and the scrutiny associated. Ideally Firefox should be funded by public funds ( like thr EU donating money to FOSS projects they use like VLC, 7 Zip, etc.). But if a browser company at it for a long time can barely survive while also having a browser that's not "fully featured"... and Microsoft, with their infinite pockets, also abandoned theirs... what hope is there for anyone succeeding at it? And make no mistake, for any browser to succeed it would need the full feature set of Chromium.
> What would be the value add over just using Chromium?
Like what the sibling comment said: [0] Until it has achieved feature parity with at least Safari, then you can talk about 'value' or realistically using this browser over a Chromium one.
I can use a Chromium-derived browser today like Brave or ungoogled-chromium and have no 'Google' in it. The SerenityOS browser doesn't even qualify to be compared with the rest on usability other than being 'built from scratch'.