FPS AND YOU
MKX is a fighting game. As with any fighting game, the game's timing is tied to its framerate. That's how we get consistent frame data. In any other game it'd be stupid, but this is how fighting games are built - and for good reason! On consoles, you can't mess with video settings. Everyone has the same hardware. You can't buy a better GPU. While people who game on the PC have many reasons to dislike this, there is one benefit: fighting games are much more stable online because of consistent framerates across players.
THE PROBLEM
If you play offline, it might not feel very different playing at 50fps vs 60fps, but the difference is there nontheless. The game is running slightly slower because you aren't getting enough fps. Offline, this isn't a problem. Whatever, the game's running slightly slowers, who cares, right? But online, even if it's a slight difference in framerate, you have two games running at two different speeds trying to play together. This creates loads of stuttering and hitching.
THE SOLUTION
SF4 on PC gets around this problem by forcing all players to run a benchmark before you can play online. If you don't pass this benchmark, you can not play online. I think that if a similar requirement was implemented into MKX, online play quality would increase greatly. Yes, the netcode isn't Killer Instinct quality, but people not running the game well is just going to make whatever lag worse. People need to learn how to turn down their settings. People need to understand that you can't expect to play new games on midrange hardware from 5 years ago at 1080 with everything maxed and expect 60fps.
WHAT YOU CAN DO NOW
Download Fraps or whatever other framerate monitoring program you want. If your FPS drops below 60 during a match, you need to turn your settings down. If it drops while you're loading or when in menus, it doesn't really matter as much. Whether this means turning AA off, turning shadows down, lowering your resolution, or lowering any other setting is going to be on a case by case basis.
TL;DR:Don't play online if you can't get a steady 60fps in-match. You're creating problems for everyone you're playing against. Everyone you play against running at a lower framerate than you is creating problems for you.