Thanks guys! For the most part, you've confirmed a lot of what I remember people saying about it.
I have a lot of reasons as to why you're all wrong
and most of them boil down to how Sticker Star works on the console it was made for. Remember, this isn't a sit down Paper Mario experience, at least not for the most part. It's a portable game, so it's elements needed to be reexamined for probability's sake.
For example, the combat. I actually liked the stickers, it made for a more card-based RPG and that was actually kind of refreshing to see. And i'd say that they're not pointless, since the means to attack are a consumable item. You get coins from fighting enemies, and the more fights you get into within the level, the bigger the coin reward at the end. You need coins to get more stickers so now, coins now supplant XP, since leveling up in the traditional sense is no longer needed.
Plus, battles were designed to be fast-paced and able to finish quickly in case you were on the bus, or in the middle of something, or whatever circumstance you might find yourself in, given the nature of a handheld device. This is why the "Perfect Bonus" works so well. You're incentivised to finish a battle in one move for a coin bonus.
Even level design is made for portability, which comes from overworld level select, as opposed to a massive open world. The levels are relatively short, distance wise so they're more about how to beat the level as opposed to how long it takes you to beat the level, solving the levels sticker based puzzle as opposed to running through a gauntlet of enemies. This works better on a handheld because it's easy to get in or get out of a level if you need to get to the sticker store, and the levels maintain the convenience of portability. That's not to say the world isn't robust enough to have interesting ideas and no two levels are the same, it's just easier to swallow, which you want on a handheld.
In a game on a portable system, which is very easy to put down and forget about, it's easy to get lost. I don't know how many times I had to gather my bearings again in "Tales of the Abyss" or "Xenoblade" because the 3DS is console made for convenient gaming. While I firmly believe games like Xenoblade can and should exist on handhelds (Golden Sun being my favorite RPG of all time) there's no denying it's a system for "pick up and play" style games. Paper Mario suits this, while maintaining it's RPG roots.
As far as the wacky and active plot, I fail to see where Sticker Star loses that, as there's all kinds of wacky antics going on throughout the game, every world has at least one interesting things going on to progress the story. It's even funnier since it's the most self aware game of the franchise and plays so heavily on the fact that everything is made of paper.
I'll admit, the bog standard "Bowser kidnaps princess for reasons" does leave a little to be desired, the world itself has enough going on that you want to see it all. Yes, the lack of partners was a real bummer as was the lack of Peach segments, and Bowser segments for that matter, but as a portable Paper Mario, I think it really works.
