Now I rather prefer solutions that have customisation in mind from start, so it's always easy to switch things.
I predict that's how we're going to end up in a few years again. Some big monoliths (whatever react is morphing into currently, plus Angular and as the world is a cruel mistress, ExtJS), plus a plethora of DOM wrappers and view libraries.
And 72 build systems.
IF you think it went the way of the dodo, I'd suggest doing a bit of better research before predicting the future :D Because IMO you are seriously off here.
I would really like to know what prompted you to fork Ember.
If you go off the rails, it is extremely painful. I haven't looked at Ember in a while, because of my experiences, so ymmv. It could all be completely different now.