2) "Every myth is true" - where every tale of monsters, gods and treasure corresponds to real monsters, gods and treasuse. D&D is perhaps the worst offender. (Evidence: Monster Manuals.) Just because some supernatural elements are true, doesn't need to mean that all tales told of supernatural elements need to be true.

3) "Fantasy kitchen sink" - related to the above, when every nook and corner is filled to brim with bizarre creatures from every conceivable mythology. It's more than a bit redundant to have goblins, hobgoblins, bugbears, trolls, oni etc. as separate species when you could have one "petty evil race living in the dark" that could explain all of these peoples.
My presonal turnoff is when people try to cram everything they can int othe setting. Like in published D&D settings - every one must have Mind Flyers, Yuan-Ti, Beholders etc. I would really preffer if most of D&d unique monsters were unique and keept on one part of the world.

4) Peoples as species - There are some fringe cases where it makes sense for all members of a single species to also be of one culture. Beyond that, there is no reason to have "woodloving hippies" be elves or "hard-working mountainfolk" be dwarves, if you can as easily have both peoples be different varieties of humans. On the flipside, each species should have multiple differing cultures.

5) Non-humans as humans with fancy hats - an immortal lich is going to have vastly different mental and physical needs than a human, and this should show. As noted above, if you can do something with humans, you don't need non-humans - so if you're going to inroduce non-humans, make them feel non-human.
Yeah, I dislike those two too.

6) "God needs prayer badly" - recently I've started to feel that the idea of gods being dependant of worship has become somewhat overused in fantasy settings. More than that, most don't think too deeply of how this actually works, which causes it to run head first into many of the same logic problems as point 1).
I belive the rammifications of that should be more explored really. Like in comics series Fables, where characters from Fairy Tales are dependant on people's belief in them - characters who are well-know and popular cannot be killed, s Snow White can take a bullet to the head and survive, but this also means that less known Fables, like Rose Red, are very vunarable and won't return to life if shot. Another thing is that it's quite territorial, which means that in Russia, where everybody knows Baba Yaga, the outcome of her battle with witch from Hansel And Gretel will be different than in United States, where latter's story is much more popular. it can also be abused - Jack Horner, who is every jack in every fairy tale, made a movie trilogy about himself and harvested his new popularity. think of how these rammifications could work in fantasy. If the power depends of how many people in certain area belive in you, gods would be very territorial and intorelat to other religions, sending their people on missions toconvert villages in other gods territorie, slaughtering their messangers and even leading crusades to enforce belief in themselves, to become more powerful. If it's territorial, no god would leave the area where they have the most belivers and would probably travel only with hundreds of pilgrims at hand, many plans would me made to kill other god into luring him on enemys theriroy, where they are weaker, and gods would meet only on boders out of fear of the other guy trying to drag them into their land ans defeat. If they can be spread by gaining followers, gods would actively do heroic deeds to convert people or send their clerics to do so.

7) No place for the natural - many fantasy setting put plain too much emphasis on the supernatural elements of their setting. But you don't need to invoke supernatural elements to convey and create a fantastic feel - just take a look at all the crazy stuff real world has.
Oh yeah, my buddy recently started gmind Deadland, that's his main complaint - behind every problem hides supernatural, it's never normal bandits who rob the train, it's undead ones.

Another thing I dislike are badly used "no stats" - characters who are said to be so powerful that players cannot match them. It's not really bad itself, I mean, Cthulhu in pathfinder is good example - power beyond anything, one that game overs you when he wakes up, because he is a very old god. Same with that giant bird from deadlands or Cain. But guys like Stone from Deadlands, who is just Revenant who made pact to get a lot of power, or that religious leader whose name I forgot - these are normal guys in that setting, jsut strong, nothing in their files puts them above players' usual level, there is no reason for them to be best in everything and have no stats.