Google will easily point you to mountains of evidence that they do work, from scientific studies. If you don't want to look at them or convince yourself you know better than the people who conducted these studies then that's unfortunate.
Fortunately, again, one more time. You do not need scientific studies to see the truth here. The goal of mask mandates was to change case curves. That was their only justification. In a large number of places mask mandates were added or removed without the case graphs changing. Therefore, they do not work. Everything beyond that is irrelevant and frequently confused, e.g. studies on masks are not relevant to the question of mask mandates.
Mind if I frame that on my wall?