The biggest flaw of this game is the lack of feeling like you're progressing towards something specific after doing the basics. You're kind of dropped in a big bunch of weird modes without any sense that they mean something. A fleshed out story mode or whatever and I would be all over that.
Writing 5 lines about 1 flaw and not mention any virtues is kinda unfair mate. This game has a stronger core than many of its siblings in the genre (imo), and variety rivalling the biggest ones.
After doing the "basics" you still have A TON of different characters, items and combinations to explore, and higher difficulty levels to keep you on your toes.