No hostile mobs appear to be spawning in my world. I am not on peaceful mode, and I have set gamerule doMobSpawning to true. Mobs like Drowned can be found in shipwrecks, and villagers and other passive mobs are appearing correctly. Also, when I create new worlds mobs spawn just fine. My render distance is 12 chunks, which is above the 10 which can cause problems. Mobs used to spawn in this specific world just fine but something changed. It could be that I slept through the night multiple times in a row with a bed.