I don't think people are saying that the PRC is economically Socialist, just that it has a Dictatorship of the Proletariat of some sort and appears to be more keen on keeping its bourgeoisie in check.
Coupled with their intent to challenge Western Imperialism (Lenin's definition), I believe this explains critical support among Marxists for the PRC, despite the many flaws.
Kinda like supporting Biden over Trump, not like supporting Bernie over Trump. You work with what's actually there, even if it isn't what you wished, and hope things change for the better.