Servo still exists and has been spun out of Mozilla's org (https://github.com/servo/servo/). Certainly development will be slower without a dedicated, paid team behind it, but it's still alive (last merge to master was 9 days ago). And perhaps without Mozilla's direct control, it will actually end up becoming the browser you hoped it would be.
I do feel like most of the arguments against Firefox boil down to either website compatibility or performance issues. Using Blink as their rendering engine would kill the first concern completely. I'm not sure if Firefox's current performance issues (real or imagined) are due to the rendering engine or UI, so not sure where that would land.
MAYBE, if you want a browsing engine / "webview".
Bad phrasing from my part too, sorry.
https://en.wikipedia.org/wiki/Gecko_(software)#Quantum
I remember it clearly because Firefox got a big performance boost in it's renderer when quantum was released, often it's faster than Chrome.
Swapping your VW Beetle's wheels for a Ferrari's doesn't make it a Ferrari! Even if it improves handling (or whatever I'm not a car person, it's just an accessible analogy)
If you compile servo and point it at the homepage of google, I doubt it renders right now. It was constantly broken even when it had a full-time staff.