My opinion on masks. We can never show in a randomized trial that masks are effective. Why? Because the trials would have to be astronomically huge in terms of subjects. Think about it. In order to prove convincingly that a vaccine works, vaccine sponsors like Moderna and Pfizer had to run trials above 40,000! No one thinks that masks could be as anywhere near as effective as the vaccines so any randomized clinical trial of masks would have to orders of magnitude larger than 40,000. Never going to happen.
That means we are left with observational studies. But observational studies are much more sensitive to biases than randomized trials. By bias, I don't mean that the researchers are biased - I mean that there could be unobserved subject characteristics between people that use masks vs those that don't use masks that explain the differences in infection rates. Especially when any true effect of masks is likely to be small.
Finally, it could be that masks have different efficacy for some viruses versus other viruses So, the low rate of flu this past season doesn't necessarily mean that the masks helped for Covid.
Bottom line is that we could argue forever whether masks are effective or not but its unlikely that we will ever know the truth. For disclosure, I wear a mask in any crowded indoor place but I don't mask outside or in low density indoor areas.