I am playing in survival on a server with my friends in normal difficulty. We have made our way down below y=0 and are exploring the new caves. It seems that there are WAY too many spawns, One can hardly walk from one side of the cave to the other without being attacked by 7 or 8 mobs. Skeletons, Zombies, Creepers, Witches, and Spiders just bombard you from all sides. At one point, I was in a small cut out in a cave that was lit up in order to take a screenshot of the new ores. All of a sudden, I was attacked by TWO creepers, one to end me, and one to destroy most of my items. Two of my friends on that server play Minecraft Java a lot, and they said this is worse than normal.

To replicate:

Start a new world in snapshot 21w08b and set it to Normal.

Go down below y=0, find a large cave, and switch to Survival.

Observe.