Forking is easy. Maintaining and developing a browser engine is really hard. Most forks that make substantial changes to the original source are either maintained by a multimillion company or die without maintenance.

But the websites aren't. If chrome is the only browser websites will target chrome. Do if you fork it and remove features that you find harmful you now have a useless lump of software.

Chrome already has a large market share and a browser changing their browser engine doesn't necessarily change Chrome's market share.

Sadly, even if you don't fork Chromium and simply embed It via Electron or Chromium Embedded Framework you still won't be able to login in to some Google sites.

If Firefox turned into a Chromium fork Google would work with them to make it work.

That's far, far from enough.