Biomes not working in Nether-like dimension

Hi, I've been trying to make a dimension with Nether-like gen, but when I add biomes they don't work. In F3 I can see that I'm in a specific biome but nothing changes, it's just the same everywhere. 

I saw mentioned the fact that the Nether doesn't have a biome generator in older versions, is this the problem? Is there something I'm doing wrong? I'm using MCreator2020.2 for Minecraft 1.12.2. 

Thanks.