It's complicated. It doesn't stop you from getting the virus if you get droplets on your hands and rub your eyes / nose / mouth, which is one of the more common vectors. So I buy that there's no evidence it stops you from getting the disease. But it does limit the droplets you spray out as you're speaking / coughing, etc. So IMO it would be part of a general solution to limit how much you spread the disease. But self-quarantine is easier to be sure you're doing it right. Wearing N-95 masks effectively is harder than just strapping it on, and the untrained are likely to touch their faces more while they're doing so anyway. I'd be surprised if everyone wearing a fresh mask properly and washing their hands properly before touching the mask or face didn't put a major dent in the pandemic. But that's just not going to happen anyway so we can't tell.

I think the big issue is supply for medical staff. There's a limited supply of legit masks. Medical staff need masks more. We need medical staff more. And the masks are more effective with training / other procedures in place. Other than that - if the masks didn't help you, medical staff wouldn't wear them.