My answer is "Every single character in MK lore can't be playable." lol
-I had to wait how long before Mileena was added to MK11?
-Ermac was not only not playable MK11, they were dead in the krypt & locked behind Towers of Time assists
-Sindel was a cameo in MKX...ONE YOU FOUGHT, BUT COULDN'T PLAY
-Shang Tsung sat out MKX
Like, I get it, it sucks. But it's also expected when there's limited spots on a roster. I'd much rather have fan favorites and a handful of 3D era characters, some new faces to keep things fresh. Than them put in characters that nobody's really interested in lol.
At least as Kameos, some of these less relevant characters are getting acknowledged. Like, as much as I'd like to see characters like Chameleon, Kai, Nitara, Darrius, & Ashrah on the main roster, if they do end up being Kameos, I won't be complaining too hard. Especially Darrius. I am quite literally the only person who gives af about that character lol. So him even being acknowledged and making it as a Kameo would be a treat.