He'll probably tell you something like "you need to edgeguard better and your fundamentals are kinda rough"
I do think you're giving Squirtle's water gun too much respect. Work on mixing up how to utilize shield pressure as well: you up smashed and dash attacked shields so often and if dirt actually punished it you'd have stopped a lot sooner and gone for some grabs. You have a habit of coming down with aerials as well. Note as well that Dirtboy is DIing your throw 100% of the time and avoiding any follow-ups. I don't know what else Pikachu has for throws but mixing that up might be effective. As for side-b: dirtboy uses it A LOT and you never picked up the counterplay of it which is really just to jump over it. You also could throw out decently strong hitboxes to break the armor on it, but jumping over and chasing down is just safer overall. Pikachu is fast enough to chase Squirtle down and punish the endlag, so do it instead of giving him free crossup shield pressure to work with. Up air OOS might be good to punish those situations as well: I believe you combo into a back air guaranteed? Correct me if I'm wrong, of course. Dirt was also catching you with the forward throw DI trap, which you just have to DI down and away to escape. Setting up techchases on squirtle is very good as well due to his really bad tech rolls. I don't know exactly how you'd go about that, but it's something to keep in mind.
I can't really comment on Yoshi as much since Snake has a really niche way of dealing with that matchup whereas the Squirtle matchup is pretty normal regardless of character.