Pit is a character that lives on virtue of his balanced matchups. As you said, he is a very well rounded character with the tools to excel against even the strongest characters in Smash 4. Because of this Pit does a great job as a secondary for various other characters since he patches up whatever bad matchups they may have. Keep in mind however that his spread might leave you wanting for more, and generally you will need to be at least of the same skill level as your opponent to consider winning. That's not to say Pit doesn't have some favorable matches either though, since his long ranged attacks and aerial superiority make him a huge threat to certain characters.
More specifically, yes Pit is worth maining in a competitive sense, but he'll require a bit of dedication if you expect to use just him as your main. Pit is arguably the best swordsman in the game because of his combination of traits lending to a diversity in playstyle, although he works best [in my opinion] as a defensive bait and approach character. It's hard to contest Pit on his well spaced attacks on the ground, and even harder in the air. His multiple jumps and lasting hitboxes are also a huge boon for edgeguarding, to say nothing of his fantastic Dair, which has a variety of uses and is one of the more reliable spikes in the game. Palutena Bow is not what it was in Brawl, but it still does its job baiting air-dodges and gimping bad or predictable recoveries. If you are having trouble against zoning characters or playstyles, than Pit will certainly help you deal with those. Between Palutena Bow (or any of his two other customs NeutralBs), Guardian Orbitars, and multiple jumps you'll find that, at the very least, those matches will feel less frustrating.