As stated in the header any MalisisCore and MalisisXY Mod keeps MC Stuck in startup when trying to run with either 1 or more of these 3 Performance-Enhancing Mods (PE-Mods):
Phosphor, Performant, VanillaFix.
Seems to be a problem with Mixins Incompatibility.
For bigger Modpacks these PE-Mods are crucial to make the Modpack run smoothly and without major issues.
Would be good to have the Incompatibility fixed
Greetings

I know that I m late with this but I found a solution.
By installing this mod:
https://www.curseforge.com/minecraft/mc-mods/mixin-0-7-0-8-compatibility
the game shouldnt crash anymore with mods that optimize the game.

I'm having this same issue. Mod works fine without those mods, but instantly crashes if they are installed (I use Phosphor and VanillaFix). As Speecker said, these are vital performance mods for large packs so while I would love to have the various malisis mods installed, I would remove them before sacrificing these performance mods. Hopefully a fix can be found. Thank you.