All the legitimate studies that did not find masks to be effective had glaring omissions, such as adherence to guidelines. Would you wear the mask properly or let it droop?

E.g. from https://pmc.ncbi.nlm.nih.gov/articles/PMC8499874/

Results: When the adherence to mask usage guidelines is taken into account, the empirical evidence indicates that masks prevent disease transmission: all studies we analysed that did not find surgical masks to be effective were under-powered to such an extent that even if masks were 100% effective, the studies in question would still have been unlikely to find a statistically significant effect.