Major issues that keep coming up are your defensive habits, in general, are atrocious.
You sidestep > down smash a lot. Way too often it looks like it's your go-to defense. Or you do it out of the blue for no reason. If Marth is dash dancing on the other side of the stage, sidestep doesn't really accomplish anything. When the opponent switched to Falco, all I could think was, "Man, if this guy could beat sidestep he'd probably be winning by a lot" and I wasn't surprised to see you get ***** that game. Your reliance on it is a huge issue; when it's not a good option you look really lost.
In addition to sidestep, I'd say you seem to attack out of bad positions a lot. And out of what seems like panic. Relax, bro. You have a big fluffy shield and an incredibly good wavedash out of shield complete with a mini-crouch for arbitrary evasion vs high attacks (aerials and certain grabs, namely). Don't panic and attack so much; you can reset your positioning and work from there.
You jump very predictably out of combos. Once it's gone, you air-dodge poorly (the goal is to reach the ground, hit a platform, or pass through a laggy move) or attack (and usually with dair and nair; add bair because it hits below instantly). Very often it is a good idea to see how far you can go without jumping, or try to bait them into attacking and then jump, or simply accept that you're gonna be hit and save your jump for a more suitable time. The way you play will get you killed very quickly versus a more competent Marth (that Marth looked like garbage).
Read my guide on comboing Marth because you're doing bad combos on him.
Your ledge habits are also very bad. It looks like roll (80% of the time) and ledgehop fair (15% of the time) and misc. other (5% of the time). Standing is better than rolling almost always at the edge because the roll gives them a lot of time to react and punish you because it's slow (Sheik's animations are so distinct; you didn't get punished much because this guy is horrible though). Experiment and use more options. Edgestall for a second to catch your breath if necessary. You usually don't have to move immediately.
I would add that you seem to hit weak bairs a lot when there's something more suitable for the situation in your moveset.
That's what stood out.
