What do you mean "lack of accessibility of Gecko"? Did you mean "lack of embedability"?
Gecko's embedability sucks ... on desktop. But that's not inevitable, it's just a matter of priorities and resources. On Android it's getting a lot better and something like GeckoView on Android could be made to work on desktop too ... if there's demand and perceived benefit.
(Mozilla's in the middle of upgrading Gecko's multiprocess support for fine-grained "site isolation" so now might not be the ideal time to stabilize embedding APIs.)
That might be true. They're all incredibly complex beasts. I don't think it matters much for adoption in terms of embedding or forking to create a new browser; the engine internals can and should mostly be hidden behind an API.
Gecko's embedability sucks ... on desktop. But that's not inevitable, it's just a matter of priorities and resources. On Android it's getting a lot better and something like GeckoView on Android could be made to work on desktop too ... if there's demand and perceived benefit.
(Mozilla's in the middle of upgrading Gecko's multiprocess support for fine-grained "site isolation" so now might not be the ideal time to stabilize embedding APIs.)