The Pits have better framedata than some other swordies (cough Marcina cough Chroy cough). Their jab for example, is frame 4. F smash is frame 10. Their back air is near lagless when landing, it’s an Inkling back air that can kill quicker than a Lucina back air.
Give the Pits better hitboxes and they would be better than most characters.
Unfortunately for Pit's jab, it's one of the moves that received a pretty significant range nerf between games (along with Samus' ftilt, a much worse nerf, and PIt's fsmash for that matter), it went from a pretty interesting midranged option (same range as Marth's jab in Smash 4 iirc--another move that got a range nerf) to whatever it is now. At the very least it had its startup buffed.
It's definitely not all bad for the Pits. They're retained or improved on several strengths between games, three notable examples being juggling, grab game and already mentioned range/frame data ratio on some moves. Nair is a really
good move and I'm always surprised to see it first mentioned in Pit's issues because of the animation. this move does almost everything--beats jumps, beats spot dodge, more than safe on shield because of its extremely generous auto cancel window
five frames after the final hit, frame 4 oos option on all sides of Pit, free platform pressure from a short hop, and combos into other moves. It also literally never fails to connect, unless maybe you're fast falling with it off stage like it's Palu's nair. As is it's one of the best nairs in the game--I think either with the improved range often suggested or by increasing Pit's air speed it would become pretty obnoxious, in the first case as an oos option and in the second since it would turn true the nearly existent cross stage nair drag combos (and off of an easy to land move). It isn't personally the direction I would choose for Pit buffs.
Besides that he has a great grab game off of an excellent dash grab. Down throw combos were buffed in this game--the dthrow dair nair combo had its window widened and it's even easier than before, dthrow nair fair dash attack (or regrab mixup) into juggle situation is a thing now, dthrow bair is sometimes a thing at later percents, etc. He also has a high damaging throw that puts you in a juggle (uthrow) as well as a kill throw. And as far as juggling he's still great, disjointed multihit uair for keeping a juggle, fast disjointed usmash for kills, and dash attack for catching landings (and if not stale then you can definitely net kills with it in this game).
Some of his moves are pretty weird and the issues
mostly lie with his hurtboxes rather than hitboxes, but in some cases it's a combination of both. A lot of Pit's animations involve lunging his arms in the direction of the move while performing it, one of the worst cases being usmash. On the first two hits of usmash Pit swings his arms above his head, which already isn't ideal since there are hurtboxes attached, but on the last hit he actually throws his entire body upwards
and extends his arm up just before the hitbox becomes active. This leads to a lot of unexpected trades, which on multihit moves are pretty unfortunate. Another example is on fair, where again Pit throws his arm out, extending his hurtbox, and the actual hitbox is pretty small and only active for a total of
three frames, one frame for each hit. Other bad hurtbox offenders here would be ftilt, bair, and fsmash.
But anyway--Pit's most significant issue is that he doesn't have any way to compete with midrange bait and punish. He can make do when he lands hits, his advantage state as I already described is good, his kill power isn't fantastic, but I think it's sufficient. He can kind of force approaches (especially Dark Pit), his nair is amazing--but midranged bait and punish is where he loses.
Think about it like this--if you're playing a midranged bait and punish game against Pit, what can he really do? Let's say that "midrange" here means just outside of Pit's dash, so that you've done your best to remove the possibility of getting naired or dash grabbed, probably his two best moves. Now what does he have left? His aerial options are basically limited to fair and bair, where both are fairly slow on startup and have relatively small hitboxes (and in the case of bair a pretty bad sourspot...), and both of these moves are locked behind one of the slowest air speeds in the game. As for ground options, he has dash attack, but neutral isn't usually the situation where you'd want to use it, especially vs any bait and punish character. Then you have dtilt and ftilt. Ftilt is almost an interesting move especially in a game where you can tilt out of dash, good range, good active frames, but it has too much startup and endlag. Then dtilt is okay, a significantly improved move since Smash 4, but here's the point where you have to acknowledge that midrange bait and punish is Ultimate's meta right now and an okay dtilt isn't enough for him.
This scenario I just described may not be possible for some characters--not all characters can successfully play a midranged bait and punish game. They may lack the right air speed, the right aerials, etc (and this group includes Pit himself). But a lot of characters
can (Peach, Mario, Joker, Wario, Wolf, ZSS, pretty much every other one of the best characters in the game). Or in some cases a character has some way of disrupting this gameplan (like charge shot). But Pit doesn't have either of these, and so he's a bad character. Buffing startup on his bair was a good first step, but it will take much more.