Mileena is NOT BAD.
Two of her specials are safe because of the pushback and make all of her strings, no matter how negative, safe on block. That shit is amazing in MK11. (ground sai and straight sai)
She has good damage, a good and easy armor breaker to use, overhead starter that travels slightly, lows you can't hit confirm but you can yolo into full combo above 20%. If you read the breakaway that's a big RIP to them.
D3, F2, jail into straight sai and that's amazing to have in neutral.
She has an advancing string that is 0 on block, another easy hit confirmable one that is +1. Another that is -8 but again with that pushback you ain't getting punished (b112).
An easy to input CG to use in neutral, on rolls, that's also her armor breaker and it's good to end combos with AND it switches sides.
Not to mention she has so many moves that switches side: Ball roll if you don't amp, F231+3, command grab, tele kick if you amp.
She has a teleport as well.
You can literally shimmy and footsie your opponent to death along with crazy good neutral moves and every single utility you could ever want in MK11. She is S tier material. The only thing keeping her from being that good is her shitty ass mid.