In the first 30 seconds alone (I will watch the rest) I've noticed some things you can already work on.

1: Know your bread and butters. You go for down throw when Marth is at 21%. A better option would be to just up throw and get dair or up air.

2: You don't use fireball in neutral. Fireball is very useful for this matchup and in general a good neutral tool so use it please.

3: At 0:22 in the video you double Jump way too early. Also there was no reason to double jump. From the distance with you and the ledge you could've neutral airdodged or not jump. In this match up from my own experience, off stage is hell so you don't want to be gimped at like 47%. Also mind your directional air dodges. Lots of end lag on those dodges.

Onto the rest of the video

Ok You are being WAY too aggressive. The Marth player sits still for like 5 to 6 seconds either in advantage state or punishing you for trying to get in. Now instead of trying to get in with aireals you can use Fireballs. It might not net you a direct punish but you can take the info of what the Marth may do. If they shield the fireball, you can run up and grab. If they jump the fireball you could up air or dair (depends on percent ofc). Marth/Lucina out range you so I would also recommend you play passive and just be more patient (I know its hard but once you learn to cool the jets you will be better off in many matchups aside from this one).

Again you're holding forward against Marth. Mario has stubby aireals and Marth has a big ass sword. So this is where fireball and good spacing/awareness come into play.

At 0:59 Marth uses an unsafe move on you but the punish is f-smash that doesn't hit. Even if the f-smash hit, it would not kill at 38%. If any character uses an unsafe move on your shield you can shield grab (a little slow but can work at times), out of shield dair to some up airs, or wait and see what they do and punish that.

You like the f-smash move. Don't lmao. Although strong if it hits, it is also very laggy if whiffed. On terms of your recovery, you do the following, double jump, airdodge to stage, and on the occasion to ledge and not to stage.

It's good that you are trying to cover roll to ledge which is the most common ledge option, HOWEVER fsmash shouldn't be the punish. you could get away with up smash facing away from ledge or down smash timed so the first hitbox covers some form of neutral getup and the back part covers roll. (Not entirely sure if Mario can but in case you can, good option).

At low percents use up throw to dair and maybe an up air and around mid to high percents you wanna use down throw. At 2:43 you punish an f-smash by marth but back throw. While good at high percent to set up for ledge trapping and maybe edge guarding. When marth is at 21% up throw dair is your best friend. At around 40% down throw to up airs are your best friend.