Here's what I noticed so far, everyone under 30 is screaming for 3D kharacters, getting rid of iconic kharacters, or going with a new cast entirely. Somehow SF has stayed popular without a lot of changes to it's original cast but added a ton of new ones. That's great for them but they don't have a genuine storyline either. It's only natural for you to be drawn to what you know, this isn't a sports team where the lineup can change drastically and people get over it over time because they know changes like that are inevitable.
You can't compare a MK to movies or sitcoms. People bring up movies when we know that changing the main character turns fans off from the franchise and that's why they reboot the whole thing. When that happens you get different actors, changes to the story(most times for the worst) and time lines. ST the original show kept most if not all of original cast and the other STs were just spinoffs not the true ST. MK no matter what name came after it was still MK and all had the OGs in it because that's who we as fans know. If there was just a blank poster with either the dragon or raiden on it you'd know exactly what it is.
So yes you can get rid of the entire Kast and still call it MK but will you lose some if not the majority of the fan base? Hell yeah you would and you'd be at the mercy of new comers to the game. Will this MK be the first ever for some? Yes, but what drives the sells are us the fans who've been playing 10 or more years. If NRS or Boon gave the 3D fans what they wanted they'd most of the OG fans, just like if the 3D fans didn't get a few of theirs in. Here's a fact that most of you keep avoiding or overlooking, the OG Kast might not be to your liking but it sure as hell is the thing that's sellin this game and made the franchise.