The main thing is that game is boring. Combat is inherently dull. It's never tense, it's never exciting, and it's rarely interesting. I run past half the enemies because I can't be bothered to shoot them, or there's too many of them, or they just keep spawning. Boss fights are a chore, and the visual indicators for damage are weak. You never really know "Should I be shooting this thing? Is it taking damage? Should I just wait around for the next scripted moment to happen? Is this a waste of ammo? How much damage does this thing do, anyway?" You fire at people out of requirement, a chore you perform to try to get past this boring level and hope something interesting happens.
And by "something interesting" they mean shitty insta-deaths like cars/trucks barrelling in where you just happen to be in the wrong place at the wrong time, or a bridge collapsing and you just so happen to be on the left side when it explodes, putting you behind a car and you can't climb out, or running from another scripted escape scene and the game takes control from you as Leon rolls on the ground from the earthquake, as a zombie grabs you and you die. Shit that's almost completely out of your control without prior knowledge, or just random luck like the falling over animation loop right into random zombie attack.
Visually, this is one of the most inconsistent games I've seen all year. Some levels and enemies look very impressive, and it's no question it's the best looking game in the series. Others are merely competent or rudimentary, leaving no lasting impression beyond recognition that yes, this is a lab, and this is a really narrow hallway. You shutter through one lifeless environment after another, doing the same things for hours. Leon's variety comes in the form of simplistic puzzle-solving and QTE-marathons ala Heavy Rain. Running around trying to find three keys while respawning monsters were cool when Chris did it, not so much when Leon does it again. The room with the little moving mines with Chris was kinda neat(even though you can run around for a minute and not waste a single bullet while the AI does everything), not so much when Leon does it again. Neither is backtracking through a really fuckin' dark cemetery where the only threats pop out of the shadows. Or running in circles in a small dark room with a too-close camera trying to find some enemies you can shoot so you can do that weak-ass shoulder throw Leon does now.
And apparently Leon/Chris section is the GOOD part! I haven't even got around to the Jake sections everybody's complaining about.
It's just a really mediocre video game, through and through. It does NOTHING particularly well, and sometimes it drops below even that standard level of shooter competency, right down into outright horrid. Spec Ops: The Line had generic, janky combat too, but at least it had a really interesting narrative and critique on game design that made it interesting. I'm at the end of Leon's Chapter 4 and I feel like I'm playing it out of due diligence. If I sat back and asked myself, "What do you love about this game, ViewtifulJC? What makes this game fun?"
I couldn't come up with an answer. I honestly don't know.