I personally don't think its very useful criticism to go around painting whole parties and movements as entirely cynical "authoritarian" facades who are just out to betray the working class.

I doubt anyone thinks that people slandering all western anarchism as either actively or unknowingly being tools of the bourgeoise state against leftist movements is a useful or even valid criticism, or shit like "Oh Anarchists are all just petit-bourgeoise individualists", but either could still be argued as a "criticism from a leftist pov".