okay methodis has a point but is waaaaay off at the same time. It's true, there's no leveling up in a regular sense, but after a few hours, "experience" as we all know it is not in star points or XP stats...it's disguised as coins. You receive a metric fuckton of coins, and at first it seems pointless. That's far from the case. Success and failure in battles is entirely dependent on the amount of coins you have. And just because you have a ton of jump and hammer stickers doesn't mean you automatically have an easy battle. You have to use coins to purchase upgrades (sticker upgrades, sticker journal upgrades, health and defense, etc.), as well as use coins in battle to string stickers together to formulate a winning battle strategy.
So basically, you collect coins to become more powerful. The more coins you have, the stronger Mario is. It's odd but strangely satisfying.
You'll tire of battles the same amount as you would tire from past Paper Mario battles. It's no different here once you realize the mechanics of them game.
Story seems a bit zzz though