Arguably, an image unseen is *also* not funny. As is artwork unseen.

The alt text isn't meant to replace the originals - it augments them so that people who can't participate in the original experience aren't entirely excluded.

A deaf person can watch and enjoy a movie using subtitles, even if the experience isn't quite as good.

If you see a group speaking a foreign language and they all laugh uproariously, having someone tell you "that guy made a very funny joke about a political leader you've never heard of" is a lot better than sitting there wondering what is going on.

And if you're experiencing mastodon via braille, a post saying "Elon after he has a poll that goes the wrong way" then nothing isn't as good as getting "popular meme showing pikachu with a surprised face" so at least you know what the joke was about.

It's about inclusivity. It's not meant to be perfect.