Drispstone caves and lush caves biomes spawn in small patches underground, making them ugly and hard to find. Most of the underground is no-biome, and this is okay, but only if when you find a biome is large enough to be appreciable. Here some screenshot. I take all screen of lush caves, because they are more easy to see, but same thing happens with dripstone caves.

So, what I suggest is to increase significantly the size of this biomes, making them much more appreciable. If needed, better increase de size and decrease the luckily of finding them.

Also, not all the underground is no biome/ small biomes, eventually you can find some bigger patch, but what I experienced is that they are really rare.