Yeah, unfortunately it is just the nature of the beast.

Ha ha, see what I did there.

I can't tell you how many Slimes I killed in Dragon Quest, Shinra Soldiers in FFVII, Octroks in Zelda, Kobolds in WOW... the list goes on and on.

This is seen in reality too. There are dogs, wolves, and coyotes in many different places. All with different sizes, colors, and behaviors. But they are relatively the same thing. Cats, Lions, Tigers, Bears, Snakes... All kinds of similar animals.

You really do see a lot more enemies as you progress through the story. From time to time you will see a a new skin on an old body with a higher level. But I would argue that FFXIV has a pretty good variety when it comes to enemies. You should notice the reuse less as you level up.