You don't have to be a top player or anything to critique. I don't even consider myself better than most of the people I give critiques. Some players I directly know are better than me cause I've played them lol.
But really like anybody can give you suggestions and its up to you to take them or not. Even if I say 8 useless things if the 9th thing is something useful to you then it's a success imo. It's pretty difficult to know from watching a couple of matches which mistakes are just random and which ones are badly ingrained habits. I feel like critiquing is largely about "just throwing stuff out there" just to touch on it in case it's worth mentioning.
Plus I get something out of it too. It's a good exercise for thinking about the game and stuff.
Anyways MT I'll edit in some thoughts for you in a bit.
EDIT:
MT:
Couple of things on stage that I think you should work on. It looks like you are moving a little too excessively. Big sweeping dash dances are setting you up to kind of stumble into peach's attacks or leaving you in a bad position to deal with turnips (usually emergency shield). You really don't want to be shielding turnips or shielding very much vs peach in general because she loves that. She has arguably the best shield pressure in the game and is more than willing to just attack your shield with fairs/nairs jabs and dsmash. I think you have a good sense of when you are not in a good position against peach, but some of your responses to this aren't the best. On the ground, rolling away is often the very best thing you can do because it can be hard for peach to punish rolls and it gets you the hell out of there and back to reset. I see you sometimes doing sidesteps which are basically never a good idea against peach (always the threat of multi hit attack, plus you don't gain enough frame advantage from sidestepping her regular attacks and will still just need to get away asap anyway.
You have a nice combo starter in the first game which is dropped by barely missing a fair. This sucks, but once the combo is dropped you just have to let it go. You end up fsmashing on a platform trying to patch the combo back together and she roll dsmashes you for it.
Whenever you get remotely out of position against peach don't try to fight it just think reset reset reset. Rolls while good on the ground are really bad on the platforms and you ate a big dsmash for that (probably just a mistake tho). When you're stuck on plats the best thing to do is just jump out or waveland to top plat because she just doesn't challenge your air game very well. Usually through some weaving across platforms you can eventually get yourself back down on the ground and back into a neutral position.
From totally neutral position she's either going to pull turnips or dash attack you basically. Here is where I would stop doing big DDs or waveland drop down fair approaching for no reason. Walk and measure your spacing against her and react to what she does. If she dash attacks, quickly DD away or shield and grab. If she goes to pull a turnip try to dash attack her or if you don't feel you can get there in time at least close the space on her quickly and try to force her into her shield and eventually punish whatever she does to try to escape.
But honestly overall you're playing pretty solidly and you would have done way better, at least taken a game, if not for your recovery. You mentioned you're not very experienced with peach and I think this is where it showed the most. You just kinda look terrified of being offstage and your recoveries are often sloppy (probably nerves) or you just simply make no adjustment to how she's trying to edgeguard you. If she throws a turnip down at you, DJ backwards a little bit to avoid that and then up B to the ledge. Don't just let that hit you and push you under the stage. If peach is killing Marth at 40 it's just about impossible to win. On the very last stock of the set for example, you should have tried to up B to the stage, and let the turnip hit you so that you could recover again. By avoiding the turnip all together you got edgehogged unnecessarily. Another time you air dodged for some reason maybe just misjudged the distance.
Towards the end in general you were floating down way way too far on stage. Against characters like Peach or Puff you need to recover "aggressively" because they could come out there and hit you and you need to use all your options and sword to protect yourself during recovery. For instance you can fair away turnips thrown at you, but you can also dodge them with a side B hesitation, sudden fast fall, or DJ if you survey that those would be better choices at the time. But by floating so far over the stage you're just kind of floating in range for her to do all kinds of stuff to you. Even though she has great offstage ability you still need to use the pit to your advantage and force her to limit herself in SOME way if she wants to come after you, which then you can hopefully respond to.
You are also DJing on stage too much. This is probably a bad habit that nerves bring on. Try to stop doing that. Don't go in the air for no reason, and especially don't DJ unless peach is actually forcing you to do it. At one point she just watched you jump and DJ in place and then just dash attacked you away as you came down for the easy kill.
I think with more peach experience your recovery will improve drastically and you'll win. I also really liked your pivot fsmashes, though they weren't always used ideally. At lower percents it would be better to punish with grab as you can rack damage much faster that way. It definitely has utility though so keep tinkering with it to find where it's best to use it.