You cannot respec Ascendancy ins POE 2 and this could be a permanant thing according to Jonathan.

U can't respect into another ascendancy

Or

U can't respect in general ur ascendancy

While the title of this post is technically true, it's not the entire story. Jonathan says they are still discussing the idea of changing your ascendancy. At the the start of early access you won't be able to and there are some designers on the team who prefer it this way, but he stresses that they will be discussing it more and it will not necessarily stay this way. It's very possible that this can change over the course of early access, especially with feedback from the players like we have in this thread.

Personally I hope they do let us change ascendancy later on, probably a little bit into the endgame. I feel like a change of ascendancy should require a bit more investment than other kinds of respecs because it's a more core thematic choice for the character.

Respeccing allowed: flexibility for those that want it, no change for those who don’t care about it.

Respeccing disallowed: forced build-defining decision for everyone, no advantage for anyone, no change for those who don’t care about it. People who want to respec or try something new may look at that 10+ hour commitment and drop their idea altogether, which feels really counter intuitive in a game that revolves around build creativity

I mean, why though? Why waste our time if we realize we made the wrong choice? I just see no actual benefit to a decision like this outside of generic "choices matter", but I don't feel like they do in this case. There are often correct and incorrect choices with a build, and not being able to fix those makes no sense. The ONLY way I'm ok with this is if you get your Ascendancy really early on, but I don't think that's the case?

I'm sure this is a hot take for the poe community, but maybe being told to start completely over for a single later-game decision you may have been misinformed of regarding your build (or simply misclicked at the time) isn't super great design

but why? sounds like a huge step backwards

I think respec should be a thing as in poe1. Imagine mid poe2 league you are done with a build and want to try something else On The Same Class. Why are we supposed to go through the campaign again on the same class to try another ascendancy? It does not make sense tbh and I believe it'll affect retention for longer time in leagues.

The only argument people are using that say this is fine is "I've never respeced ascendencies anyway" lol