And in both these cases I think a reboot is warranted.
In MK9's case there was too long of a backlog of bullshit through all the games up to that point. Making the games unfriendly for newcomers. Thus MK9 going back and retelling the major events through the timeline fit perfectly to bring a new generation of people on board, and also allow them to continue and finish the saga through 10 and 11.
With the ending of 11, there was nothing further that could be done through that thread of timeline so in this sense it makes sense to reboot sort of with a MK reset while also not being the same obviously as characters shifted into new roles hints that the timeline isn't completely reset. But it seems like this is meant to be a new "starting point" for people just not getting interested in the games.
That's all well and good, but they already have three starting points now.
Deadly Alliance was a starting point for a soft reboot by killing off Liu Kang and adding in a whole bunch of new characters. Midway screwed up on the storyline, in addition, Armageddon story and gameplay sucked total balls. Then
MK9 was the second starting point. I get it in that part makes sense, but titling is still stupid. Just call it a reboot and move on. With
MK1 being the third starting point, but in a reset universe that Liu Kang desires. At that point, it's just an alternate universe. Drop the number and just add some type of subtitle. All it does is make it chronologically more confusing and you got to differentiate which one.