Very few mobs spawn in caves, especially small or medium. I can walk right into medium open caves and expect few mobs. In 1.16, there were many more mobs to fight in the caves even though they were smaller. This makes the game discouragingly easy even on Hard difficulty and feels unbalanced as there is much less danger walking into a cave now than 1.16.

It is NOT resolved, the screenshot added by the other user shows the issue. A couple total creepers and zombies in a large cave is too small of a number.

To replicate;

Find a small or medium cave in while playing survival and observe the amount of mobs inside.
There will be much fewer than before due to new caves lighting themselves up with glow lichen and lava removing spawnable spaces. Not only this, but with the new light level rules, this eliminates quite a few spawning spaces.

Please note this may not occur every time due to varying factors, but it happens more often than not and makes it too easy.