Masking has never been sufficiently proven to be effective against the spread of respiratory viruses. For SARS-2 specifically we have one randomized controlled trial, DANMASK, which showed no effect of masking (note the primary endpoint was self-infection not community transmission, but self-infection is a decent proxy, and furthermore community transmission is incredibly difficult to study, which is why it is so evil to me that the public health establishment convinced people that "my mask protects you, but not me" when there's actually never been evidence that it protects others as evidenced by the utter lack of studies on that part specifically)

For the pre-2020 studies, they were more or less in agreement that masks didn't help, even in healthcare workers, who tend to be better trained and more compliant with masking protocols. Indeed Macintyre et al provides strong evidence of the risks of cloth mask wearing; while this study compared cloth masking to standard practice, not no-masking, it at a minimum establishes the very real risks of cloth mask wearing: https://pubmed.ncbi.nlm.nih.gov/25903751/