I only knew of Dublin Core as it relates to image metadata. I was told it was popular among photo-journalists (it has tags: publisher, keyword, creator). The more nerdy EXIF metadata is what the camera often provides and tells you about how the image was taken (f-stop, shutter speed), not who or what.
Now if there were some universal standard for embedding alt-texts into a picture that would also survive right-click "copy image" and paste-uploading... not just for social media (where you'll get blasted for forgetting one even just one time) but also for websites and newspapers where the image description has to be edited manually in a CMS and is, again, not attached to the picture itself...
I work with alt text a lot. I used a hinted LLM prompt for the first pass, and then I edit if needs be. Sometimes it misses obvious details, other times it sees things (most) human eyes would never see. Like all tools, just have to be careful how you use it.
