I don't get how a character that is heavy we can't catch in the air doesn't have to fight on the ground and can combo uss did even. It's definitely slight wario favor on a neutral stage. Worse on a wonky one
Diddy is really fast on the ground and has so many options which makes it really difficult for Wario to choose the right approach/whatever he wants to do.
I know he can camp Diddy decently, but Diddy ***** any appraoch Wario has. His grab and fair are really good in this MU.
It's always such an uphill battle for me with Wario vs Diddy... and with Diddy it's not too bad. You just need to overwhelm him with your speed. It's not easy but still doable. Just keep in mind Wario has to be really careful too.
Also you can definitely trap/catch Wario in the air with Diddys good groundspeed/bananas.
And yes, Wario doesn't approach from the ground often, but he's not MK. He has to land like everyone else. That's the point where you can catch him/his landing. And don't say bike or something because that's easily interfered with too.
He is heavy and can -theoretically- kill us really early. So we have to be cautios while he has the strong fart/we're att KO percent for it. Wario doesn't live tooo long too btw. He's much easier to KO than MK or someone like that just because he just can't play safe enough... (he can run away but will be catched at some point and if he is he lacks the options MK would have and such)
Also I'd rather avoid close combat against Wario. Staying out of fsmash/grab range is good. Spotdodge is annoyingly hard to punish... and fsmash/fart are scary.