I'm just coming at this from my experience as an artist. Moogles and their designs change depending on the game and its art direction. It is indisputable.
So while moogles look like this in FFIX, which is has a chibi art style:
The traditional moogle design makes sense and compliments the games art style.
Whereas in Final Fantasy XII, they look like this.
In a game with as many different humanoid races as XII, a moogle design like that makes sense. If XII's moogle looked like the traditional moogle in IX, it wouldn't gel with the world as much because it doesn't compliment its art style.
Realistic does not mean any less fantastical. Behemoths look realistic but they're pretty fantasy-based. I'm not sure how a cat with a ball antenna and wings will be any less fantastical just because it's realistic.
It's not a "mentality". It's just basic art design.
A game that looks like this:
Has little reason having moogles that look like this:
It's not a "mentality". It's just common sense. It doesn't mean there shouldn't be moogles, but redesigning moogles to fit the world a bit more, would be expected. I'm not sure why that's a controversial statement given that's how moogles and chocobos have always been handled.
In FFIX, chocobo's look like this because it's a more cutesy game.
Compare to XII which is more realistic and the chocobos are bred for war purposes:
Same concept.
Are Final Fantasy XII's chocobos any less fantastical due to their more realistic design?
No.
So don't argue that FF15's moogles would be less fantasy-based just because they're treated more realistically. It is, after all, still a flying cat. There's nothing realistic about that concept on this Earth.