You may be thinking, upon seeing my title, "Gee, isn't that harsh?" ...no.
As you are all aware, many game mechanics were replaced for this installment of the usually-renowned Paper Mario series. What you may not realize, however, is the actual quality and execution of these replacement mechanics. There is no easy way to say this- everything is half-butted and unintuitive, the polar opposite of a good Paper Mario game. Or heck, a good Mario game.
Take the Things, for example. At first, they appear to be the replacement for pretty much every advanced field move and partner ability from previous games. However, whereas with those games, one could use these abilities an endless number of times, here, Things can only be used once, period, regardless of whether it's on the field or in battle. This is a problem since you could accidentally waste a Thing you need to progress and either backtrack to where it was found or rebuy it again. A simpler fix would have been letting Things be used without leaving the Album in exchange for either adding a secondary meter or even using up coins.
Let me address the Mega Muth in the room- the game never tells you important details to beating the game, such as environmental entrepreneurship (using the environment to figure things out, due to a lack of actual substantial gameplay mechanics). Nor does the game ever really explain boss weaknesses before it becomes a problem, or imply weaknesses before getting to the boss room (like in TTYD). I'm not talking about "handholding" as certain types of players try to twist it- there's nothing wrong with having a little help.
Speaking of that, Kersti is useless. Unlike the Goomba partners from past games, Kersti giving useful info is the exception, rather than the norm. This uselessness is really pronounced in a late game stage, where she blathers on about how paper fares in a certain environment instead of giving actual useful info.
Finally, battles. Due to a lack of a third unique type of reward only in battles, besides stickers and coins, there's no point to them. Why not make it so that, for every 5 HP knocked off the other side in battle, a sticker can be powered up...and have enemies give out more coins? That would give way to a new dynamic.
The irony is how, in purposely getting rid of the story, IS subconsciously half-butted it everywhere else.