Mostly because I'm thinking, "Oh, I've seen this again."
So the Rhino was cool. Gwen Stacy is mostly cool. Electro had some cool parts, although he slipped from "dangerous misunderstood person" to "insane cartoon villain" wayyyyy too fast.
But the whole "I can't be with you because of my enemies" thing? Bored to death, who gives a damn.
Oscorp? NO. I just do not give a damn about Oscorp anymore. Harry Osborn? NO. Just stop it. We just saw this shit a decade ago. I think the last trilogy had something like the "Oh, Peter Parker sometimes takes pictures of Spider-Man, therefore they must be best friends" thing.
Another thing I don't care about: Spider-man's origins. Do you realize that the ENTIRE "Peter's Dad" subplot is essentially MEANINGLESS? There was something like 45 minutes devoted to that, and all we got out of it was that "Oh, the genetically engineered spider only gave Peter powers because of a weird coincidence with his dad!"
SO WHAT? They added a bunch of layers of complexity to the origin, only to tie them all up in an essentially meaningless knot!
"Maybe Peter's Dad was a traitor!" "Oh, no, he wasn't."
"Maybe the special spider venom could cure Harry, or cure other people of stuff, or give them powers!" "Oh, no, it was hardcoded to the Parker family line."
"Hey, Peter's father was uploading a MYSTERIOUS FILE to a MYSTERIOUS LOCATION, I bet it's important!" "Oh, no, it's just a video saying that he isn't a traitor, and that the spider venom won't do anything."
Useless.
There is a reason why people think Spider-man 2 was the best Spider-man movie. It didn't clutter stuff up.