I agree with the sentiment. But the main reason I have heard from browser builders is that Gecko isn't as easy to integrate as Blink. Nyxt browser, for example, is engine-agnostic. They still have trouble integrating Gecko. Servo, on the other hand, is designed with embedding in mind. They have picked up some pace after joining the Linux Foundation. Libweb (Ladybird's engine) is also a candidate. Let's hope that current situation spurs them on.

I'd been under the impression that most of the useful stuff from servo had already been integrated back into gecko, but I just checked their git and was glad to see that development continues, despite mozilla's layoffs