I mean, sure, mechanically speaking, it's very polished - low animation priority, responsive movement and aim. But in terms of combat encounters, it's still very horizontal and there's no verticality whatsoever. While I've only finished Act 1, I can't help but feel that Gears is stuck in the past and is afraid of branching out from its stop-and-pop shooting roots. Sure, Act 2 is open-eneded/sandbox in nature, but going by your impressions, it seems like this aspect isn't well-integrated into the game's core design and ends up being barren and uninteresting.
I'm playing on the Insane difficulty, and essentially breezed through Act 1, thanks in part to the weak AI and fairly generous checkpoints. My favorite bits so far were imitations of things we've seen in The Last of Us. For example, JD's foot getting caught in rubble and the camera presenting his PoV from upside down as he has to shoot down an incoming horde of locust. Ring a bell? Or how about those latent/sleeping robots (read: clickers) that can be stealth killed from behind, but can also enter an aggressive woken state if they're alerted. At some point during development, someone at the studio must've thought about half-heartedly adding some stealth for the sake of variety, without incorporating any actual stealth mechanics.