My main issue with Dark Pit is that he does actually have some potential for a unique moveset with different weapons from Kid Icarus Uprising still being available. Sakurai just decided to make him basically a clone of Pit with very minimal changes aside from Side Special, voice, Final Smash, and a couple of other things. Having a different personality than Pit doesn't make him different enough to say that he's not basically an outright clone of him, because that's what he literally is, just with Pit's repressed feelings as his personality, and a black and purple color scheme. Blades, Palms, Claws, Cannons, and Clubs are all other types of weapons in Kid Icarus, and if Pittoo was able to use the Electroshock Arm in his moveset despite not using it in Uprising, then he sure can use weapons of those types too.
Basically, I'm just really bothered by the fact that he was an outright clone in Smash Bros. when he had a good amount of moveset potential. If he were Luigified at least, then I'd be happy with his inclusion. And yes, character slots aren't a thing, yadda yadda, I'm just still dissatisfied with him in Smash 4.