People often cite the failure of Edge/Trident - even with the resources of Microsoft, it's still impossible to compete with Google.
But there's a big difference between "competing with Google and taking significant market share away from Chrome" and just "writing a browser engine that supports the modern web and runs on personal computers". The latter is definitely not impossible.
I wish them all the best, but you can't hold up some half finished project as proof of feasibility.
When you realise that change is their weapon, and that they've been successfully convincing web developers with propaganda that the latest is the greatest, the latest features that only work in their browser, while at the same time deprecating features that existed for possibly decades before in all browsers and providing essentially equivalent functionality, you'll see the truth of the situation.
It's not "embrace, extend, extinguish"; it's "embrace, extend, extend, extend, extend..."