Disinformation actors and tankies complain about the left all the time

If you want a genuine answer, people are upset because you're expressing a centrist opinion. Centrism more or less advocates for maintaining the status quo. The status quo sucks for most people.

You're also equating the far left with the far right. To understand why this is upsetting, we can look at some basic definitions. If someone is on the Left, they are generally in favor of more equality, while those on the right want more hierarchy. Equality and hierarchy are opposites. You can see this in a more concrete way by comparing the goals of far-left organizations to the goals of far-right ones.

I think a lot of the confusion comes from the Cold War. Countries like the USSR and China would claim to have far-left intentions while acting in right-wing ways. You cannot achieve left-wing goals through right-wing action.

Even the term "Communist country" is an oxymoron, because Communism advocates for a stateless society, and governments never voluntarily give up power.