This game is incredible. It's hands down my favorite game of all time.
I see people complaining about the story mode being bad, or complaining about some franchises being overrepresented, or complaining about not getting the DLC characters they want to be added to the game, but I don't really care. The story mode was extremely unimportant (to me, at least), and I doubt most people actually played it through to the end. It's true that franchises like Mario, Pokemon, Fire Emblem, and Zelda have a lot of characters/clones compared to other franchises, but I think it's fine since most of them are still fun to play. I always see people complaining about online, and I do admit that it can be bad sometimes, but it's usually fine for me.
Not only can you play this game competitively, but it's also the perfect party game that anyone can quickly pick up and play. There's so much to learn and practice in this game, so I'll never reach a time where I think I've mastered the game completely. I've spent hundreds of hours into this game already and I know that I'll spend thousands more. 1000/10.