It's worse because unlike the lightning dodges where it's just a matter of getting in the zone and... managing to stay in the zone the entire time, here the speed at which you need to hit the ball keeps increasing, and the timing for those last few hits is incredibly strict, so you need not just to maintain your focus but also be both very fast and completely precise for those last few ones. Thankfully I gave it another go a few hours after I made that post and actually managed to beat it after a handful of tries (oddly enough being kinda sleepy actually helped somehow). I know if I were to try to do it one more time it'd probably take me ages again, so thankfully that's over with.
I'd never played a Mario & Luigi game before, but while the gameplay here is very fun, I have to say it's jarring how the other Mario RPG games I've played (the two Mario + Rabbids ones, The Origami King, Super Mario RPG and The Thousand Year Door) were all super amusing and full of charm and personality, this has just... none of that whatsoever. Not a single likeable or interesting character, not a memorable or funny line of dialogue, it's just incredibly bland in that aspect. Sometimes it goes for wacky but it just lands on nonsensical and stupid rather than actually entertaining. It's especially noticeable as I beat The Thousand Year Door like a week ago, a game which has absolutely top-notch writing and a brilliant cast of characters, from the party members to random NPCs you came across in towns, and that was what made me want to play this one after, as they play fairly similarly, and the two games are basically night and day in terms of narrative. Again, the game is still very fun to play and that's enough to make it enjoyable, but it's wild how much the ball was dropped/how little effort went into that department.