Well, and it depends on the mask.
These newer variants are so contagious that to protect yourself from being infected, you need a well-fitted, high filtration mask. Anything less effective than an N95 (and assuming you don't have a beard or moustache) isn't going to offer a lot of protection from other people's infections.
If someone is sick and doesn't have an N95, covering their mouth to avoid coughing and sneezing is better than nothing at all but the longer you are in a confined space with them, the higher the chance you'll be exposed. Over the past 3 years, I've been exposed more times than I can count but because I had on an N95 and I've stayed current on boosters, I haven't tested positive. Knock on wood.
The people that we're seeing with symptomatic COVID have the same qualities in common: they didn't get the 2024 booster and they were indoors in a large group of people (especially holiday gatherings of family members) recently.
And keep in mind that because we have a significant population of people who have COVID but aren't sick enough to stay at home and we have another group of people who don't know they have been infected who are exposing other people.
March can't come soon enough.