[1.16.5] Passive mobs spawning in newly loaded chunks even if gamerule doMobSpawning is false/World frozen

I just started a new survival world, and i accidentally set the gamerule to false, but i saw some passive mobs spawning and literally freezing my world.

I couldn't enter commands, attack mobs, mine blocks, and double blocks like tall grass didn't collapse when broken.

 

P.D: i am using an almost 300 mods modpack, and has been running really bad lately. I even set more memory to it. I had to set 1.18 because i can't submit 1.16 bugs anymore.