I understand where you're coming from, but there is a very strong reason to disambiguate, for leftist theorists: plenty of us still want to strive for a communist society, which we view as the best way to organize ourselves.
It's perfectly understandable that one of the mechanisms used against this philosophical and political ideology is the modification of language to win rhetorical battles, but... we're going to push back lol.
Let's try this and see if you can relate: America is actually a socialist country. Between farm, airline, and oil and gas subsidies, oligopolies defended by regulation, and the seizing of the assets of society for the bailing out of banks, the American economic system is a far cry from capitalism. All the innovations that came from this economic system called American socialism we can attribute to this firm socialist organization of production and consumption. America is successful and a good place to live, more countries should strive for socialism.
Surely you see how frustrating this would be? Thus how many leftists feel when we argue for concepts we like about communism as it has actually been defined for centuries vs the rhetorical twisting done through necessity by Stalinists, Maoists, and McCarthyists (all in different directions, mind you). It becomes much harder for us to have conversations about the actual merits and values of a given system.
To whit: how can we describe a society that's achieved our goals of communism, if we use the same word to describe a society that's the opposite of our goals? Ignoring tankies for a second who have lost themselves in the sauce and pretend that the Soviet Union wasn't plagued by famine or that somehow the PRC is a socialist paradise despite the fact that they still pay for healthcare, can you see how difficult it is when I say "I want the shared resources of society to be leveraged to provide for people's basic needs, and for workers to be empowered to enjoy the full fruits of their own production, I want communism," and for two different people to say "You want communism? So you want (repeats definition of fascism)" or "You want communism? You want (repeats definition of capitalism)".
I get tired of words losing their meaning. If living int he PRC is "living under communism," what shall we call a system with common ownership of the means of production (the State, made of unelected officials, owns much of the industry in the PRC, but, some of it is privately owned by billionaires), no private property (the PRC has this in many ways, especially when owned by corporations), no social classes (the PRC has massive income divide and insurmountable socio-economic classes and poverty traps like much of the modern world), no money (the PRC runs plenty of international banks, and the basic needs of citizens are still paid in cash), and no State (need I explain the power of the State in the PRC)? Because that's what communism is, so I have no idea how to even have a conversation when the word is made to mean something else entirely.
Say it can't be achieved, say it's unrealistic, say it can only be achieved if xyz horrible thing happens, that's totally fine, that's an interesting conversation to have, but we can't have that conversation if we can't even settle terms.