But my understanding of Pit the character is so nonexistent I still can't tell what I'm watching. Like, I can watch a Diddy or Sheik and understand what they're doing, even if I don't use them myself, but I watch Pit and I'm just like "...huh, that happened" half the time.
Well, that's the price everyone pays when there's a select group in a spotlight. Hell, people are still confused on what Diddy's doing and can do. It's just with characters like Diddy, Fox, Sheik, ZSS, Luigi, and sometimes Rosalina - I only know Dabuz's Rosalina -, people have some basic knowledge of what they can do.
Look at aMSa's Greninja, Abadango's Pac-Man, Nairo's Zelda, Ally's Mario, etc., people just don't know them because there aren't a lot of those characters being played which leads to misconceptions, confusion, and early write offs. You do not know how frustrated I get when I listen to commentators say Falco can't do anything. Sure, they have to say things on the fly, but some commentators just throw out things and it leads to a lot of issues for people watching. The idea that Falco can't edgeguard, can't kill, can't combo, Dair is useless, etc. frustrates me and it extends to others like Ganondorf, Ike, Link, Toon Link, etc. Their reputations in previous games and early impressions kills them: "Marth's nerfed", "Meta Knight's nerfed", "Peach is weaker in SSB4", etc. Ike for one gets consistently placed low tier despite his ability to combo with strong attacks as heavyweight, his Fair and Bair auto-canceling, and people generally agreeing Ike's a monster with customs. Oh well, I digress.
Disclaimer: I don't know Pit as well as Pit mains, so take what I say with a grain of salt.
The run down for Pit is this: Nair, Fair, and Uair combo. If anything, Nair and Fair are used like Fox's Fair out of D-throw or Palutena's Nair and Uair comboing or Fair to push people away. Dair is mostly for spiking and along with Fair's range, Bair's tippered hit, and Pit's multi-jumps, Pit's edgeguard game is good to say the least. And Pit can Gentleman his Jab.
Dtilt is good from what I hear, Ftilt is great for spacing and it kills well since it has a tipper hit which Dark Pit doesn't for some stupid reason, and Utilt can combo, but I don't know about its range. Up Smash is wonky since Pit can miss at pointblank with it. I don't think he'll miss with Rosalina since she's taller, but on say, Mario, he might whiff the entire move, Down Smash I don't really know about while Side Smash has good range, kills well, and it's one of the fastest Smashes along with Samus, Dark Pit, Marth, and Lucina's.
Palutena's Bow might not have major use in this MU, but he can arc the arrows, so he could go over Luma or aim directly for Luma. As an edgeguard tool, it's probably more annoying than anything. Upperdash Arm is what makes Pit "worse" in this MU than Dark Pit since it launches people up rather than at a 45 degree angle which, I think, kills Luma sort of like how Captain Falcon's Rapid Jab finisher launches Luma. Guardian Orbitars can gimp certain characters like Ike who would just gets pushed back when using Aether or hit the Orbitars and enter freefall. I don't think Rosalina will have a problem, especially with that fast custom. Still, it might be better to not get send off stage and recover well since mistiming it could launch Rosalina into the Orbitars instead of the ledge. Power of Flight has an issue where if Pit's too close to the ledge, he won't grab it and instead, just goes above it, so he'll need to go a bit deeper for that. In other words, if Pit messes up his jumps and gets too close, but just far enough that he needs to use Power of Flight, Rosalina should be able to spike him or just wait after his Power of Flight screw up and Utilt him with Luma.
F-throw will kill, but that means Pit needs to face the ledge, D-throw combos as with pretty much every D-throw, B-throw's your standard B-throw, and U-throw I'm not sure, but I think he can combo out of it.
This is dated, but you could watch Jtails's video on him and Dark Pit:
https://www.youtube.com/watch?v=nR1Znxxa_hA.