From previous snapshots it was mentioned that the generation of Ghast in the Valley of Souls was going to be regulated, but since the 20w18a the generation of Ghast was lowered to the point that it was almost non-existent in the biome.
The reason for my complaint is also due to the good reputation that the biome had before 20w18a, which was considered, in a good way, one of the most difficult biomes in the game, and one of the most fun for players who love it exploration, PvE and Technical Minecraft.
Just as it gave meaning to the "Speed of Soul" charm, since it was used to facilitate the journey through the Valley of Souls.
In conclusion it is a change that I consider necessary for this great Update.