As I don’t personally benefit from transcriptions (except in extremely rare cases where my colourblindness becomes pertinent), I’d say asking the folks over at c/main@rblind.com would probably give you the best answer, but I can give my take as someone who has been doing transcriptions for a few years.
I think that including a transcription when you have the time do so is always better. It’s never possible to say who might be interested in experiencing the content (and it’s not just blind/partially sighted people who are helped out by transcriptions; see section 1, here for a non-exhaustive list). I an say for certain that there are people who benefit from and want them; when I was part of the (sadly now shuttered) r/TranscribersOfReddit project, we did receive requests for transcriptions of purely aesthetic pieces.
I think that, though the minority that can’t view the image will be even more pronounced here, transcriptions are essentially another way of including more people in experiencing the same “scene”, if that makes sense, even if they’re doing so via a different medium. As just one example, that could include people who previously enjoyed the community, but became blind/partially sighted and still want to experience the content in some way. Obviously it’s a bit subjective, which is usually something we try to avoid in transcribing, but I try to write transcriptions of art or scenic photographs with the intent of capturing the atmosphere of the image rather than with purely clinical descriptions as I might in other situations, while still including all the actual details of the image.
That said, obviously detailed transcriptions take a fair bit of time, so it’s definitely not a mark against anyone who doesn’t include them. I find myself doing a lot less of them these days as well. I would say this is one of the circles where transcriptions are less pertinent, but I think it’s always a good thing to have more ways of accessing content.
If one does ever get created, I’ll definitely try and remember to ping you!
To answer your edit questions, which I’ve just seen:
The original r/TranscribersOfReddit (ToR) was run by an actual non-profit organisation (the Grafeas Group) with a lot of infrastructure built up to support it and keep it running smoothly. When Reddit’s API changes happened, we didn’t have the resources to move the project somewhere else (and nowhere else was as dreadfully inaccessible as Reddit), so we were essentially forced to shut it down. The communities that exist on Lemmy aren’t coordinated, they’re just people who used to be part of ToR doing transcriptions in their free time, in a capacity not associated with the Grafeas Group. As such, there isn’t really a way to coordinate them.
I just sort by new on the communities I’m subscribed to.
I don’t use a screen reader but l do know the answer to this – alt text on the image is a much better route to go when you have the option, as it means people can find the transcription right next to the image instead of looking for it in the comments. Helping people find our transcriptions in the comments was a challenge on Reddit.