Just let it die. We need something new or at least a CEO with a vision that is not steered by the tides of LinkedIn hype
A new browser engine is an incredibly hard thing to program and historically they have always been financed by multi-millions (now billions) companies. Even Firefox via Google.
If you want another engine that is not WebKit or Gecko and you want it open source, you are asking for something that the free software community failed to deliver for the last 30 years and that is harder to deliver everyday.
If Firefox happens to die, we are basically stuck with a Webkit-only internet. We may have open source browsers but nobody is going to pay for the Gecko development (which is not just maintenance but keeping it up to date with the web specs) and nobody is going to pay for a new engine.
With multiple engines that have a big enough user base, you force the actors to negotiate standards.
What will you do with your fork when Google will start to implement a replacement for HTML like they tried to do with Dart or AMP ? With enough competitors, Google is forced to make those unilateral evolutions backward compatible with what works everywhere.
With only one engine they can force their new tech in the engine and bet on the fact that it will be integrated in the forks because it’s mostly one pull request away on GitHub.
Maybe that would work if the fork somehow managed to evolve as fast as Google on Blink. But this literally means that you need Google’s kind of money amounts.
You also probably say you hate "Cancel Culture" while cancelling things including coke.