Well, most of what we'd have to go off of would probably be Twitter, and let's be honest, probably not the best metric. Twitter comments give themselves to outrage and people have noted that it doesn't exactly bring out the best in people.
But into the EXP issue people have complained about. It got me thinking, and EXP can be difficult to balance. The worst offender being a necessity to grind, however there is also the idea of how many enemies are you expected to fight? All of them? Most of them? Even then, in Paper Mario in particular, level ups were not the greatest thing. You only got to improve one stat per level up, and it was never a direct attack boost. It also seems to be a tendency of younger players to pile on the HP. While that may work just fine in Mario RPG and Mario & Luigi where other stats go up anyway, in Paper Mario that can be detrimental in particular. And, honestly, I'm not the biggest fan of how level ups worked in the first two anyway. Sure, the small numbers may be delightfully simple, but I honestly didn't always care for the choice though it got better one I just decided to do them in order even if that isn't optimal. Honestly, of the three Mario RPG types, they may have been the least important in Paper Mario anyway (perhaps better in SPM) given how gradual the increase could be outside of badges.