> But you have to use a forked repo of forge and gradle to do that.
Thats the toolchain im referring to. You need to make changes to make the toolchain working in the modern world. some people have hacked the old versions of the tools to function. But the better option is to build the tools to use the old version's data. Specifically updating https://github.com/MinecraftForge/ForgeGradle to be better.