(This belongs in some other thread so it'll be my last post on the topic)Without Close Combat though, Kommo-o could not take advantage of Dragon Dance because it’s best fighting STAB was Sky Uppercut which is objectively weak. It was in RU prior to USUM.
Okay, I'll humor you with Kommo-o's lack of Close Combat being the reason it was RU prior to USUM's release. It certainly had nothing to do with it getting an omni-boosting, offensive Z-move that complimented its naturally impressive bulk and useful defensive typing (which help to aid set up opportunities with later Dragon Dances). It definitely didn't involve it getting Drain Punch, a STAB move weaker than Sky Uppercut but offers it a form of recovery, which is especially nice when boosted by Belly Drum or (to a lesser extent) Dragon Dance. It also probably didn't matter that it got Stealth Rock, offering it an interesting niche when combined with its defenses and typing.
I don't have any particular problem with Kommo-o learning Close Combat, honestly. It's just that the move existing invalidates almost any other possible physical Fighting STAB a Pokémon could want (and that's impressive, given that Fighting has 3 other physical STAB moves with 120+ base power, 4 if you include Reversal, and another 4 that are 100 BP). Sky Uppercut has been one of my favorite moves conceptually since its introduction in Gen 3, and I've always been saddened by its low distribution (I also wouldn't call 85 BP "objectively weak." On the weaker end, sure, but it's not a weak move). Kommo-o getting it was finally a chance for it to see some love, I thought, and then they went and tacked CC onto its learnset in USUM. Incredibly disappointing.
There may have been multiple reasons behind them cutting Return/Frustration; most likely they're just a pain to keep at full power and aren't mechanically reliable. But I also think there may be some merit to them cutting the moves for the strength of a STAB option it granted Normal Pokémon. But, if that is the case, there's some definite hypocrisy in removing those attacks but adding CC as a TR now.
And don't get me started on the hypocrisy of weakening the long-time 95 BP Special moves to 90 in Gen 6... and then introducing Moonblast for their shiny new Fairy type, complete with 95 BP.