Thank you response makes more sense to see where you are coming from. Early on in the pandemic, the CDC was asking people to not use the N95 masks because supplies were low to nonexistent and they were needed for the front line workers. Not that they were ineffective.

PPE use was foreign to many people. Using inappropriate materials, wearing it under your chin, under your nose, ill-fitted, unsanitized removal procedures, not following basic guidelines. That's why there is failure. Human behaviour.

But, masks and PPE are effective combined with social distancing. Even people in 1918 understood this method to help.

This is a good primer and has links to several studies
Still Confused About Masks? Here’s the Science Behind How Face Masks Prevent Coronavirus

The paper that you reference is a meta-analysis (talking about trying to stay published. That paper is a case in point.) I've commented specifically on your other post...