Like a lot of things, "mask effectiveness" means one thing for an individual and another for a population. If everyone wears a neck gator while walking around walmart picking their nose, it's probably not gonna be real effective. If an individual wears a properly fit mask, they probably won't get covid.

Covid causes brain damage that lowers your IQ by about 7 points [1]. That's probably why China was going to great lengths to prevent it from spreading domestically. I still haven't gotten it, probably because I wear a vented N95 in most crowded places; I've long since given up on wearing a mask to protect other people who won't bother to wear one, but a fitted ventilator does lower your risk of getting the virus if you care to avoid it.

[1] https://www.thelancet.com/journals/eclinm/article/PIIS2589-5...