Lol wtf it's not about "looking fly." It's about using those techniques to continue combos while they are still in hitstun or improve your spacing. Wavedashing with Mario isn't godly, I never said it was, but it is USEFUL. Whether it be to create distance, juke, or close distance, whatever. If you can use a wavedash or a waveland to gain that extra distance to follow up with a bair or nair or something, then do it, because Mario can use those techniques quite effectively to keep things going. Spacing properly and using fireballs and dash dancing is a given. I'm not saying wavedash or waveland all over the ****ing stage because #swag or else you will get punished for doing it unnecessarily (especially with those extra lag frames that you mentioned) if you aren't paying attention to what you're doing and making bad decisions like using them to approach all the time or doing it too much that you leave yourself open because of lag. If you use them intelligently then at least from my experience they can be quite beneficial to his combo and spacing game. Mario can waveland off of platforms and dair, fair, nair, or bair while dropping down for example (you know, from a read or something like that.)
Look, I'm not trying to sound like a ****, but your post sounded so dismissive of the potential that waves have. The amount of frames is irrelevant if your playing smart. I use waves a lot when playing with my friends, and it has definitely helped me create larger combos and improved my spacing. I used to be reckless too, until I got wrecked for it all the time and I learned. It's all about how and when you use it. I hope that cleared this up a little bit, or at least clarified on what I was meaning in my post, because I think this was a misunderstanding.
As for pressuring shields or OOS, Dair to dsmash on shield can apply pretty good pressure as the dsmash will push them away if they are shielding still. If they don't shield it it also doubles as a pretty good combo, and if they DI out of dair you might get them with the dsmash when you land, or you might push them away if they shield it when they escape. Just remember to be safe and don't go for more than you think or you can afford. If they escape the dair and roll away, you probably don't want to try for a dsmash.