Nothing wrong with MMOs. The appeal is that you have other players who are all shaping the world, ideally (Ultima Online). Unfortunately, most developments in the genre are moving us further away from this model (instancing everything, no player structures, private messages and chats instead of messages appearing overhead, no player interaction, etc.) Failing that, PvP in MMOs can be quite fun because it involves far more diversity and strategy than PvP in any other genre (e.g, moba, UT-style shooters, Counterstrike-style shooters, etc.) It's a good combination of long-term planning, non-PvP effort, and PvP skill. In addition, there is often a lot of space for fun financial schemes in MMOs.
I haven't played any mobas, but their appeal is clear. The difference from an RTS is obviously teamplay. In RTS, it's usually duels, as far as I know.
CCGs are fine too. If you pay the regular price for a game (e.g., about $10), you get a decent deck. The appeal is that you can use this limited array to beat players who have clearly been playing the game for longer or who paid more. Sure, a player who invested more money might be able to beat you, but you should treat as playing on higher difficulty rather than being 'non-competitive'.
I don't enjoy the following:
2D platformers - too actiony, feels dumb. The new hipster wave of these is even worse because it is not even challenging.
3D platformers - as above, but also infuriating controls.
Counterstrike-type shooters - run around for ages until confrontation, die, do nothing for five minutes. Annoying subculture, too.
Plot-driven shooters - a bunch of cutscenes with rudimentary gameplay.
3D action games (e.g., Assassin's Creed) - as above.
Truck simulators - I tried a couple, and they were like hiking simulators but with awkward controls.
Other simulators (e.g., planes) - I understand the appeal of detailed simulation, but it bores me to death because I am not interested in all that technical stuff.
Racing games - get old after about 2 hours.
Diablo-type games - far more similar to the characterisation of MMOs in this thread. Grind, grind, grind. The builds may be interesting but ultimately pointless because the PvP is rudimentary.
Puzzles - very boring, the gaming equivalent of cross-stitching.
JRPGs - melodramatic cutscenes with rudimentary gameplay. I'm also allergic to the visual style in most of them, especially the SNES cutesy type.
Most adventure games, especially the modern 3D ones - cutscenes with item collection.
In short, I generally dislike most genres out there. Looking at game lists on Steam et al. fills me with a palpable sense of boredom.