I’m not saying taking gecko and modifying it is impossible, just far less pleasant than taking blink/V8. Ladybird is interesting because it’s a completely independent project from chromium or FF with some really nice ideas. I hope to see it succeed but seems to be moving a little too slowly as a project to be a serious contender. That’s all to say it’s far easier to make chromium based browsers than FF based browsers. FF has needed a rewrite for like a decade already.