I beat all of the stories on professional, and I absolutely saw why people hated it. Between enemies being able to lock you in corners, bullet sponges EVERYWHERE(don't get me started on fucking Simmons and Ustanak), and literally every boss has at least three or more bullet sponge stages to be fought in. It stopped being epic by their first stage and fights in general drag on for way too long to be entertaining anymore. Bosses started pissing me off more and more, and my thought when I died wasn't "damn, maybe I should've paid more attention," instead it was "damn, I have to do all of that again?" Bosses are so tedious and they even recycle their movesets when you see them again with their final forms being exceptions, but they're still just giant sponges in the end.
The health bar being a set of cubes doesn't help either. It's dumb and it's impossible to tell whether an enemy is going to take out a cube with a single hit or.. a quarter of a cube? So you're always chugging your herb flavored tic tacs even when you don't have to because you can't tell how much health you really have.
There's also every single action movie cliche in the book. Avoiding moving trains, shooting an exploding barrel in slow motion while in a moving vehicle, taking cover in a cabin, escaping explosions by a hair, airplane crashing, "YOU killed my father!" plot twist, you get the point. Everyone is acting so serious during the entire thing as well. I know Resident Evil isn't known for any good narrative or characters, but RE4 realized that by making all of the dialogue laughably campy. RE6 cranked up the edge dial to 11.
I do appreciate the mobility given to the characters though, and the melee attacks were very satisfying along with the visible body damage from your shots. Being able to finally move and shoot gets tested a lot during your fights and I liked how they at least TRIED to incorporate puzzle elements into it. They're all pretty easy puzzles, but puzzles nonetheless.
I'd give RE6 a 6. It's a little above average. Not much though.