Yeah, the ancients would have almost certainly failed in Ultima Thule. Seems they have too much aether to interact with and manipulate the dynamis there, but not enough to personally fight and win an aether vs. dynamis sumo match at the edge of the Universe.
I picture it as sort of, lets say you get 10 points to spend. The Ancients went all in, 10 on aether, 0 on dynamis.
That point distribution wasn't going to work for the threat they were facing, so we all got chopped up and remade and now we've got a 3 in aether and maybe a 2 in dynamis. Yeah I know it's a little unfair we lost 5 points along the way but it was kind of a long and messy process to get us to this point

, was still good enough to win in the end though.