I actually kinda felt the same way too. Though I would describe it as a solid series that doesn't hooked me right in. It does use a lot of standard shounen troupes but it does it well. So, I won't called it "mediocre"…It's actually a series I would recommend to others funny enough. My younger brother love it.
I dropped it after the tournaments arc (or in the middle?). Even with the spoilers around, I still don't feel inclined to catching up with it. Everyone is loving the series so much and I'm just "I'm not really getting it". Lol
I was kind of same but lately manga went into "starting to become solid read" with less fancy designs that I didnt liked and more of character and world building that interests me.
Stain was turning point for me. When I started it I hoped for series that will give me "The Incredibles" feeling and boy I was dissapointed as time passed but lately(again - since Stein shown up) it became solid experience that does not drop under some quality and has some peaking moments. Maybe its not same league as bigger series but with some more world building, new ideas and so on it eventually can get there. One Piece captured me after around 200 chapters in so what we have with MHA has big potential. You should at least speed-read through some more of this stuff.
What currently is happening has me hooked - in all departments.