Here I am, wearing masks for many hours a day over the course of many professional years. And not once have I suffered from oxygen deprivation or carbon dioxide retention.
Because that is not a thing.

Here I am wearing cloth masks made by my wonderful mother so that I can run non-medical errands without wasting supplies needed for patient care.
Thanks, Mom!
(She made about a hundred of these for members of our community. For free.)

This is my youngest child who suffers from pretty significant ADHD & anxiety but still wears a mask to protect our community.
And she can multi-task. https://abs.twimg.com/emoji/v2/... draggable="false" alt="😊" title="Smiling face with smiling eyes" aria-label="Emoji: Smiling face with smiling eyes">

A well-fitted n-95 can filter very small particles. It can be uncomfortable, leaving marks & a very sore nose. What it can’t do is filter molecules like oxygen & carbon dioxide. So while I’m cranky in this photo, I am not hypoxic or hypercarbic. Even after wearing this for 12 hrs

In conclusion, stop your bitching. Cover your face while in public to help keep your respiratory droplets to yourself.
Be more like Laurel who knows that you can be a good neighbor & a kind friend just by wearing a princess mask.