Lemmy.ml is the instance admin'd by the developers of Lemmy, who are Marxists. Lemmy.world is admin'd and moderated by liberals who generally are hostile towards Marxism, and have defederated from the 2 largest explicitly Marxist instances as a result.

Users generally prefer Lemmy.ml or Lemmy.world depending on their opinions on Marxism and Communism vs liberalism and Capitalism. We are on Lemmy.world right now, which is going to have far more people agreeing with OP than if this was posted on Lemmy.ml, where users hold the opposite opinion, that Lemmy.world is a problem (generally).

They do not support the Biden administrations genocide in Gaza.

Sure. They're not far enough to the right for some of .world's centrists, who are very upset that some people from .ml are outspoken opponents of genocide. And as such, they have for the third time designated an instance to be the "tankie instance" that they desperately want .world to defederate from. .world's centrists will continue this until they have convinced the admins to defederate from .ml, at which point they will once again find a new instance to designate as "tankies" and start the pressure to remove it.

They consider .world's neoliberalism to be the leftmost acceptable boundary of political thought, and will do anything to limit the discussion accordingly.