This reddit thread is full of comments along the same lines as the negative steam reviews:

"The ending and act 3 in general was massively disappointing"

"Glad to have read this. just finished and super disappointed"

https://www.reddit.com/r/BaldursGat...se_disappointed_in_the_endings/?sort=new

...

I suppose that's all we can really do when we dump hours into something we're emotionally attached to only to feel empty in the end. Seek support groups, commiserate.