The limitations of keyboard input are one of the primary reasons why fighting games have always found it difficult to be a niche on the PC market. Using the controller overall is just going to be better because the game is designed that way. The "tap tap tap" of a keyboard versus digital and/or analog fluidity of a game controller is a battle that always goes in favor of controllers with newer fighting games. Hell, I even find the input lag on PS4 to be really off-putting with a controller at times, so I can't imagine how bad it would be on a keyboard.

Older fighters however (for example - the original MKs) benefit from the hard input of keyboards in ways controllers cannot, which makes certain special moves and combos easier. For example, in MK!, I can duck with Johnny cage, and while still holding down, do the back, forward low kick input and launch a shadow kick right out of a crouch, which is nearly impossible with a pad.

I definitely hear you - there IS input lag on the keyboard that is very detrimental to MK11. I advise trying to just master using a controller.

MK doesn't listen to left input ('A') when you're holding right ("D") since on a controller you can't input both simultaneously. however that just makes landing back-forward special moves more difficult when you're facing left. (there is a fix to this)
About your problem you can just check see if your inputs are being noticed properly as they are logged out in practice mode

Hi i have 2 usb keyboards (one mechanical) and both have some imput latency compared to xbox controller (even Bluetooth).

I did some test in games, tryinge to do actions at the same time. The controller always hit first.

Not only in MK11. I noted that is SFV, Injustice 2. Anyone know why keyboard seems to have more imput lag than controller?