I guess you've read that shared post by @Stormgren. Image descriptions are not only good for blind or visually-impaired people, but they're also good to help sighted people understand an image which they wouldn't understand without the description.
"I have no interest in your topic, and don't even read your posts, but you violated this rule that I arbitrarily made up, and I will force you to change even if your actual followers don't even want it."people may still cut into my reach, so I can't ignore them. Besides, they don't enforce rules which they themselves have just pulled out of thin air right there right then. They enforce rules which the greater Mastodon community has already firmly established, and which Mastodon is expected to live by. And when I say "Mastodon", I mean the typical Mastodon user's perception of Mastodon which includes everything that happens on Mastodon, regardless of where it comes from.