Remember when Paper Mario was about the story, the unique and amazing cast of characters, charming worlds, and a very fun battle system? Well say goodbye to that, as Paper Mario: Sticker Star is just a game where you run around, collecting stickers and things (yes, they are called things), and having a lackluster battle system, mixed in with bland characters and a bland story.
First off, the battle system isn't good. Stickers are what you have now, and they are your only form of attacking. Also, you can only attack the front-most enemy, giving battles an unnecessary in-depth thinking.
When you use a sticker, it's gone forever, and when you run out of stickers? Run. And when you win a battle? You just get coins, no exp at all, and you can find coins plentifully around the map, meaning that there is absolutely no point to battle.
To get stickers, you just run around the map to find stickers, and you better save them, as bosses are the only use they have for, otherwise you're dunzo.
Also, there are things (real world items) you need to find to progress, which tie in to puzzles, which the puzzles are very cryptic, forcing you to refer to a guide very often, whereas the previous installments, you only needed a guide for certain secrets, not fullblown progress to finish the game.
By the way, I played Paper Mario: Color Splash (the next installment in the series that followed the same forumla as this game) and I had to refer to a guide multiple times to progress through the game my first time through, and that's even with hints the game gives you, so I can't imagine how bad the puzzles are in this game.
And then, the way to beat the bosses that are tough? Just use an OP thing sticker and win, or finish them off with one or two stickers, giving absolutely no strategy whatsoever, coming off as lame.
Second: The levels themselves aren't that great either. They are just bland, featuring a grassland, desert, toxic forest, snowy mountain, etc. The levels don't feature something that makes them unique or memorable, except the boo mansion level, that was lit.
Third: No unique characters. It's just basic Mario enemies and toads, except now featured in color! Also, Kersti is quite annoying as well. And the main villian? It's Bowser! And what does he do? Kidnap Peach in this boring character plot and design!
Fourth: The story sucks. It's just Bowser kidnapping Peach, no character development whatsoever.
And lastly, the thing that gives this game a 1 star? The fact it ruined Paper Mario as a whole in terms of the fans and the game series. We now have one side saying the latest 3 games sucks, and the original trilogy is amazing, while the other side say that all games are pretty much equal in their own right, giving us a pretty toxic fanbase. And yes, this game caused the next two games, Color Splash and Origami King, to follow in this games footsteps, and instead improve upon and not going back to the amazing original formula.
So if someone says, "This game doesn't deserve the hate it gets." or "This game is overhated.", Paper Mario Sticker Star does deserve the hate it gets, as it caused a massive mess in the Paper Mario series and fandom, and is a mediocre game at it's finest.