it's not that weird for me. mario rpgs are starter jrpgs and are short, but very straight-to-the-point, linear, focused experiences. we're not going to get 100+ hours epic sagas with tons of sidequests typical of the genre with the mario franchise.
that being said i would love for mario rpgs to have actual post-game content regardless. most post-game content and sidequests are just tedious fetch quests (like the trouble center in ttyd or koopa koot's favors in 64). jrpgs and other adventure titles (such as majora's mask) have their own stories embedded in optional side quests for example that don't really tie into the main story and i think having little story arcs like that would be fine and dandy and fit nicely in a mario rpg, and could also expand on side characters such as mario's partners as characters.