Its also sub optimal speed to lag a bit so a blue shell doesnt blow you up, but since its a mario style cartoonish video game you often find that the optimal play isnt to have the smallest or biggest number at all times.
I would say any change that makes mario cart less like mario cart and more like other racing games is a change that makes a worse game. A racing game that involves more strategy than the rest is more interesting than a racing game thats just more cartoony.
I think lagging behind for OP items is less interesting than a skill-based race.
In a party environment, those OP items are great. Bullet Bills help the new player spice up the friendly environment. But if the pro is lagging behind specifically to get OP items, I think that makes it less fun and less interesting.