Make certain biomes more rare

I have made a datapack that generates small islands not too far apart from each other on a vast ocean using this tool right here https://snowcapped.jacobsjo.eu/, as well as other ones. Now I want to make certain biomes, that are spawning too much, more rare like mushroom fields and all frozen oceans but whenever I try to either make them rarer using the same tool or even completely deleting them from the pool they still generate the same way they did before. Do I need to change something else on my files so that certain biomes are more rare?