If you want to learn how to do accessibility, specifically alt texts, properly, this guy does it exactly right.
I'm a screen reader user and don't encounter those often. There's even some fun in those alt texts, i.e.
"screenshot of unicode character inspector revealing "epic" to actually be "еріс". of course you, a screen reader user, aren't fooled."
Btw, most people would just label that "screenshot", which is extremely infuriating.