NetherRealm Studios is "working on" raising the 30fps cap during sections of Mortal Kombat 11 to 60fps.
Currently, close-up animations such as fatalities and fatal blows, as well as the entire Krypt mode, are capped at 30fps, but the devs want to provide "the option to increase the caps in those areas to 60fps", they said in the latest patch notes. They promised more details "soon".
You can already raise the cap to 60fps thanks to this mod, which also works on ultrawide monitors. However, the mod doesn't work very well in Krypt—hopefully NetherRealm will have more luck.
If you missed Matt's Mortal Kombat 11 review, check it out here. He called it a "deep, customisable fighter" that's accessible for new players.