I'm just going by what's written in the book.
There are literally a dozen or more flying opponents at every single Challenge Rating in the Monster Manual. So, yes, flying opponents are pretty common. If you were to remove every flying creature from the Monster Manual, the Monster Manual would be pretty darn slim.
Again, not doing things "directly against" the mundane character. Is using a stirge giving the finger to a mundane character? Giant Eagle? Any of a thousand other flying critters in the game? There's exactly ONE monster that can cast Anti-magic Field in the Monster Manual and that's an Archmage. Which doesn't even have Anti-magic listed as a spell. The DM literally has to change the monster to do it.
As to the rest of your post, I'm sorry, but, I cannot understand what you are trying to say. Could you state your point directly, without resorting to examples? I'm having a reading fail.