The CP critics, oftentimes, suffered from the very failings that you mention. In contrast, _artists_ in the CP -- e.g., Tillie Olsen, Bertolt Brecht, Tina Modotti, Pablo Picasso, Sergei Eisenstein, etc. -- & more broadly artists within or close to the Popular Front culture -- e.g., Langston Hughes, Duke Ellington, Orson Welles, Luis Bunuel, etc. -- not only were not hostile to modernism; in many cases -- _especially Brecht, Picasso, Welles, & Eisenstein_ -- they were the best embodiments of modernism, whose styles _& theories_ have continued to influence artists of later generations (including artists who are un- or even anti-Marxists).
Even the quintessence of literary modernist _excess_ Goerges Bataille was briefly part of the Popular Front!
Yoshie