Ehh, I don't think MK3 was THAT bad lol. I mean MK4 in a lot of cases was worse IMO, MKD and MKA have infinites that are easy as pie. Kabal didn't tone down much from MK3, he's still a top tier in UMK3 but Sub HAD to be toned down. His clone=insane ownage.
I'll admit though Subby was way too powerful in MK3, but besides having the final version of MK3 in UMK3 I also believe it was made due to lack of popular characters a la Scorpion, Kitana, Mileena, "the mysterious Ermac", Smoke, Reptile, Mileena etc, etc.
A lot of fans complained that they wanted these characters in MK3, so they were put in UMK3
besides polishing the game up a bit and doing more balancing.
When Midway gives themselves a long timeline, they make good games.
UMk3 very good game, MK
A good game, Psi-Ops great game etc.