New Super Mario Bros. 2 and New Super Mario Bros. U aren't exactly games I would call "Underrated", but there is one aspect about them that I do feel people who have disdain for those games don't give enough credit.
When you stop and look at the overall gameplay, it is the gameplay we came to know and love from Bros. 1-3 and Super Mario World. Just updated with new moves and more.......smoothed out? Is that a hot take? I do remember Mario World feeling a bit more stiff when I went back to it after playing NSMBU.
Regardless, the gameplay of the New Super Mario Bros series did accomplish the goal of giving us main series 2D Mario on newer systems.
Remember how long Sonic fans were starving for something like that? Granted there wasn't as long a gap in between Mario World and Mario U as there was between Sonic 3 and Sonic Mania, and Mario had more main series 2d games in between those two while Sonic did not, so I can at least see merit in the argument that the next main series 2d Mario could stand to have some new mechanics.
Either way though I do kind of feel like what NSMB 2 and U did right with gameplay gets glossed over by it's scorners because said scorners are too focused on being annoyed by the re-used level themes and bosses.
Though in their defense, I would like some new ones of those things next time as well.