How exactly would Marx denounce Lenin? Or Mao? That’s a supremely goofy statement.
Bakunin was not correct in analyzing power. If saying “states have issues” counts as being “correct” enough to only approve a system that has only ever lasted a few years at a time, you’re intentionally missing the forest for the trees. The USSR was by no means perfect, but it was history’s first true Socialist state and managed to prove that Socialism does work.