Personally, my biggest problem with the film was just how jumpy and fast paced it was. The camera angles were all so upfront and in your face and I just wanted to watch a lightsaber fight where I can fully comprehend what is going on like the ones in Episode 3.
My second biggest problem was the ending scene, I get what JJ was trying to do by including it, but it just kinda annoyed me more than satisfied me.
Third biggest problem (spoilers), the force healing was not the right way to go, it created so many plot holes in Star Wars and I personally found it a bit lazy, there were other ways to depict Kylo Ren losing/dying and Ben Solo coming back and sacrificing himself.
Fourth biggest problem was how easily Rey defeated Paplatine. Felt like I was watching a school play to be honest.
To be fair though, JJ had an impossible task in writing this movie and I think he handled it as best as he could with what Rian left him. I just hope Disney can successfully bring back the Star Wars type films we know and love. I don't need nostalgia from old characters, just give me a film that feels like Star Wars with interesting and well-built characters I can get behind.