Man i really need to learn how to quote but @ Posty. I just now saw your post bro, so sorry for the late response. Honestly my marth in his Melee prime was way better, and honestly I don't like Project M marth because it just seems too different from the Melee version. I'm actually in the process of creating a new playstyle for myself with him in PM.
At this point, I wouldn't even say my Marth is good. But if you want my opinion ill give it to you. First your Marth is too predictable, it wasn't that My marth is good or better, it was just I was able to read yours moves and then predict your next actions before you did them, so I adjusted based off what you did and then acted. Like when you ledge hop to wave land grab ( I was impressed when i saw you do it the first time especially considering the minor lag) but after you did it the 2nd time I caught on to it and found a way around it. You should have more than one approach for any given situation, just incase someone starts to figure you out you can switch it up on them. And honestly you're not the only person who has that problem. Ever player I have fought online in this forum has that problem too.
Your Marth reminds me of the old original meta game before Ken Invented the way we should play marth today. For example the walk up forward smash right off the respawn capsule. Not many people are going to get hit with that. Or the way you run straight at me and dash attack, You should dash dance abit before that.
And my marth is can only play at about 50% of his best online. Because of dealing with lag. So I usually stick to less risky movements and edge guards.
Sheild Breaker hits under the stage, so I like use that and D tilt, is pretty safe too. If your fast you can d tilt to pivot, wave dash back to edgehog. But I can only do that sometimes online. I think you should be able to pull that off pretty well.
I think you should dash dance -> <- -> grab/dash attack or run at them waves dash ( if they block, grab them) if the spot dodge dash attack them.
I hardly ever saw you wave dash back forward smash ( which is basic bread and butter for marth ) the above inputs works well with this too.
You should shuffle N-air through your opponent shield to pivot grab to counter their attempt to shield grab you.
That's pretty much it, all of this is basic marth stuff, but with the way you play now you and alot of players have to watch out for what we call in my town " Sharingan Players" players who the longer you play against them the better they become against you. I'm actually one of them, thats why I've been able to 3/4 stock alot of people i have played here ( everyone except matt and dead, and obviously anyone i haven't played yet). The best way to counter us, is to not stay on the same character for too long. The more you switch it up, the better.
I'll be gone for a few hours, good luck mate.