Atm10, only zombie piglins spawning on cursed earth and no blazes and wither skeletons.

Title. I made a mob farm in the nether but it doesnt spawn anything other than zombie piglins.

Im thinking it has to do with the biome because it is redstone abyss from regions unexplored. Is that the issue?

And is there any other way to spawn mobs via a spawner cuz i dont want to rebuild the mob farm somewhere else unless i have to :( .