It's not **AS** disappointing as it could be.
**For one, the more important reason:** Though both Yasuo and Akali already got skins this year, both of them were quite poorly received. Battle Boss Yasuo's skin was called okay but boring and pretty uninspired at best, and a pixel-filled mess at worst. And Project Akali, along with Project Jinx, was considered perhaps the worst Project skin ever, what with her messy color scheme, model, and overall thematic, whether it was justified by the skin lore or not. So really, this could be considered more of a Blood Moon-K/DA Evelynn situation, where she got two skins in a year but her fans were so disappointed with her first post-rework skin in Blood Moon that people were perfectly fine with her getting the much better K/DA skin. I know we haven't seen True Damage Akali or Yasuo yet, but we can hope the same is true for them.
**For two:** This hasn't been confirmed or denied yet, but it's quite possible that the live performers chose the champions to get their skins, though the champions probably would have had to be chosen from a certain "pool" that would fit the theme. So it's possible that we might need to think of these as more of a World Champion team skin-esque situation, though we still don't know whether this is true or not. But if it is, it would certainly justify these picks even more.
Now are Akali and Yasuo still disappointing choices, despite these points? Oh yes. Especially Akali, since she just got K/DA last year anyway. There could have been Diana, Leona, Taliyah, Twisted Fate, Quinn, maybe even a crazier pick or two like Tryndamere or Xin Zhao (though we don't know exactly what kind of music this will be yet, so take all of these with a grain of salt). I think Ekko and Senna look great, and Qiyana is fine; since she's new, I think it's alright for her to get a second skin even though she was only released some months ago, and the skin itself looks pretty cool. Maybe even better than her Battle Boss one.
So yes, I don't think Akali and Yasuo should have gotten these skins, BUT, there are points that might justify them getting them. So for all those out there who are fans and/or mains of Akali and Yasuo who were disappointed by their overwhelmingly disliked skins earlier this year, perhaps this will be Riot's way of apologizing.