@AlinaLeonova
Two things. First: Oh my god, my toot is full of typos. I'm so sorry!

Second: The IPTC standard enhances the metadata information stored in a pictures Exif tags. One of the IPTC field is a caption/description field. Or in short: There is the possibility to store alt-text in pictures metadata and we should use it. We as in we, the users, but also as in Fediverse, the client apps, the server software, etc.