Way too late for this. Sorry but its not like changing the kind of tires on a car. You code your netcode into your fighter you code it DEEP. Its less like if you have bad teeth and replace them with dentures that work better and more like if you have nerve damage; you can't replace a nervous system because its tied to everything else that interacts with it. Netcode is like the nervous system .It is highly unlikely they can just swap out the entire system ever. They can only really work to improve upon the stability of what they have now.
While it's true that it's too late to change something as integrated as netcode, and the best we can hope for is to tone down the seriously absurd nput lag and terrible matchmaking, it's kind of a misconception. GGPO was designed to be bolt-on netcode, and developers honestly overstate how difficult it is to implement.
MKX is a bit of an exception to this since it doesn't seem to use a standard 2d game engine (hitboxes drawn over the models) and instead uses a 3d style per polygon hit detection. (or it feels that way with all the character specific whiffs/juggles) But any game using the Street Fighter/KOF/KI standard 2d hitbox interactions can add GGPO at almost no cost. (This is why it was implemented in Vampire Savior/SF2HDR/SF3SOE/etc) It would have been super easy to put in MK Kollection but that was a horrible nightmare that sucked so.
Remember GGPO was designed as a fan thing to just easily let you play classic fighters online. Also Skullgirls, which has the best implementation of GGPO, is a game made by a tiny studio for 5 platforms. So don't go saying it's only doable on single console games. NRS has more people working on doing sweat effects on Cassie's Uniboob than the entire Skullgirls or KI teams.
The real reason that some games have it and this one doesn't is due to the developers priorities. Remember that KI and Skullgirls both had lead designers who were tournament players. Kiets/Mike Z. For this reason the games were made from the ground up with tournament play as the priority. Notice how few extraneous modes those games have, sure it's partially due to their small teams, but it's also due to the fact that their their priority is a game that can be played online and offline at a high level.
Mortal Kombat X and (Until very very recently) Smash Bros are on the opposite end of the spectrum. They are first and foremost games aimed at a casual audience. They are full of "fun" extra modes. They have deliberately non competitive features, they spend much more time on things like story modes or single player content. While they have tournament modes and in the past few years the developers acknowledged them, the entire game isn't focused on high level play.
In this type of game online play that replicates offline play simply isn't a priority. For low and even low-mid level players the game is about pushing buttons, getting in single hits, jumping around and fatalities. Frame perfect punishment, optimized combos, even anti-air and reaction blocking are not something they care about. For these players 10 frames of input lag, while it might feel a little unresponsive, is basically invisible.
These are the players who are defending the online on forums and in reviews, because to them the game plays the same offline and online. If you aren't using strings and just mashing out special moves and d2 the game is perfectly fine online. Most of the time your special moves come out an d2 is practically a safe poke in this online cesspool.
Also in the community for this game they outnumber tourament players 100 to 1. So why cater to us? More costumes, more guest characters, more fatalities. Nerf things that feel bad to casuals online like Kano 2.0 and leave things that are high execution but destructive. (Like Kabal) It's crappy but we are not the real target audience.