I would guess you are overdriving density in the shader. Try turning it down in the shader. If you need more, add density to the simulation, don't try to boost it after the simulation. You'll just fill up the voxels to their edge, which creates the blockiness you see.
Edited by Enivob - July 7, 2022 08:40:36
Using Houdini Indie 20.5 Windows 11 64GB Ryzen 16 core. nVidia 3060RTX 12BG RAM.