the art style of modern solar-punk is largely based on earthships

One would certainly wouldn't get that impression by looking at most solar-punk imagery. Nor does the imagery reflect any aspect of the dispossessed that I can see.

when did i claim that inhabited island was foundational media for soviet sci-fi art?

You brought it up as a contrast to me pointing out discrepancies between solar-punk art and what the dispossessed describes. If you agree it's not foundational to Soviet art, then what relevance does it have to the discussion?

is there another piece of soviet sci-fi you want to use instead as an example for it being more realistic and plausible than the dispossessed?

There are plenty of examples of Soviet sci-fi that are more realistic and plausible than the dispossessed because Soviet sci-fi was rooted in a real-world socialist system that actually existed as opposed to a purely speculative one the dispossessed describes. Here are a just few prominent examples from the USSR that offer plausible (within their era's understanding) visions of a futuristic socialist society:

• Andromeda Nebula by Ivan Efremov where Efremov, a paleontologist, meticulously details a future Earth (around the 22nd century) where humanity has achieved a truly global communist society.
• The Noon Universe Series by Arkady and Boris Strugatsky presents an advanced, peaceful, and technologically sophisticated communist society
• Alice Selezneva series by Kir Bulychev paints a consistent and plausible picture of a future communist Earth