I don't think EVERY card in a set needs to be consistent with a theme in order to have one. Roaring Skies, Furious Fists, etc. aren't 100% sky and fighting themed, but they're enough so to when you look back at them, you remember "hey, that's the set with all the flying types that's in the sky and stuff!" or "That's the one where a bunch of buff pokemon beat eachother up in a boxing ring"! It doesn't have to be 100% to be thematic. Small subsets are only done perfectly because of how condensed and small they are, to where they have that ability ot be 100% working on a theme.There's really not been many main expansions that had consistent theming, especially not in English where they combine 2-3 different sources that don't mesh together. Even a tiny set like Jungle had random things like Clefable, Mr. Mime, Electrode, etc tossed in despite not fitting the so-called "jungle" theme at all. lol
Only the smallest subsets like Southern Islands, Double Crisis and the Radiant Collections got it right.
That being said, I think that Sun and Moon takes the "Not all cards have to be thematic!" thing a bit too far and makes sets completely muddled and unmemorable. It's like you said, them shoving 2-3 sets together that don't fit. I wish they'd slow down for once.
Like Frost said? It'd be pretty much just the popular stuff. It's easy to forget that you're in a minority of an opinion when you're in one. I would argue in terms of sheer representation this generation does Ultra Rares better than the last few, but that's just me. I think they're actually being more diverse in that sense. It's a shame though, that we're getting this in the Hyper Rare and Gold Item generation where the amount of set bloating muddles the fact that Honchkrow and Shuckle are now getting Ultras aside the popular favorites. It's a nice touch in my opinion and one of the few pros this gen has.If only the customers got a say in what Pokémon get new cards...