Certainly, to me, the game felt a lot like being on auto-pilot. That was mostly because of the "Witcher senses" mechanic - because that's exactly the kind of gameplay I prefer over combat.
I would likely have ADORED the game if I'd been challenged mentally by the quests and especially those detective segments. That would have been a really fun challenge for me - and I absolutely hated that I was simply clicking red stuff without knowing why, half the time.
Atrociously bad game design - but, again, a concession most likely based on not wanting to scare away the casual audience.
I'm not embellishing anything here - and I truly felt like I was going from cutscene (dialogue sequence) to cutscene with minimal personal input, beyond the occasional C&C decision.
I can't stay engaged by that kind of drone-like gameplay and even though I was loving the story - I ultimately had to give up in complete boredom around halfway through Skellige. I did last ~100 hours, though - which is a true testament to the quality of the story.
As for combat, I'd say if you play on anything except Death March - it's definitely more of a button masher than the previous two Witcher games. I started out on the second hardest level (forget the name) - but I switched to Death March because I never felt challenged.
Naturally, this is only true if you're an experienced RPG player who're invested in developing a powerful character.
I imagine the game might well be reasonably challenging for people who literally just mash buttons without caring about creature strategies and patterns.