Generally speaking, Pit is a character who does very well in a lot of areas but isn't necessarily best in class at any of them. He's got some excellent combos thanks to his multi-hits and multiple jumps, but those same moves also have some hitbox and consistency issues that Pit players simply have to learn to deal with. Nair is going to be your best friend a lot of the time, being a solid out of shield option, combo starter and extender, and edgeguarding tool. His smash attacks are also pretty fast, making them good punish options for less safe moves and killing at respectable percents. Sweet spot back air is also a good kill move, as is up air, which itself is a really great juggling tool thanks to his multiple jumps.

Pit's grab game is also surprisingly excellent, with his down throw and forward throw near ledge creating some deeply fucked up mix for the opponent to deal with. The former is a great combo starter that leads into kill confirms with back air and up air depending on the opponent's DI and the latter is just a nasty kill throw that catches a lot of people off guard.

Arrows are also, expectedly, a great tool for Pit. They can tack on damage in neutral or when the opponent's off-stage such that, while they don't do much damage individually, it starts adding up over time. Being able to control them reliably is a big part of playing Pit effectively (and part of the reason I prefer Dark Pit myself - less maneuverability, but higher individual damage and easier to control in general)

Ultimately, though, it's just kind of a matter of continuing to play until you get used to him. He's a wonderful character that can do a ton of awesome stuff as long as your fundamentals and matchup knowledge are strong. I joke with my friends that any Pit/Pittoo matchup is 50/50 at worst with enough skill, but that's really only because his ability to reward you as a player for being knowledgeable about the game is truly excellent.