The biggest issues have already been mentioned by others but I'd just like to add - there's a lot more climbing in Forbidden West, but the mechanics feel a lot worse (to me anyway). I found the climbing in HZD boring but serviceable; in HFW it just feels awful, Aloy never does what I want her to do and I regularly plunge to my doom for unknown reasons. Also the pullcaster (basically a grappling hook) is super clunky to use and adds essentially nothing gameplay-wise, just some random superfluous interaction points. It feels like there might have been some cut content there.

I enjoyed Zero Dawn quite a bit - the hunting and fighting mechanics in particular - but Forbidden West is kind of a sidegrade at best. It just feels like a sequel for the sake of a sequel.