This seems where our opinions diverge
If you are posting a screenshot of the game, for the alt text you would describe what is pictured in the screenshot
Unless the meaning is in the picture, all the alt-texts for gameplay screenshots would read "gameplay screenshot".
I like the example on the wiki. An alt-text for a company's logo would read "company logo" and not describe that it is a half eaten fruit with bite marks.
Alt-text is not a transcription of what is seen in an image. It is text that is displayed, if the image cannot be rendered. It is recommended to use this mechanic to make it more accessible for people needing a screen reader. But the purpose is still to display the text if the image is missing, so people not seeing the image know what the image is supposed to show. It is not meant to be a textual replica of the image. And it is not fixing the design of a page without barriers, if you do not design it with that in mind from start. Repurposing this for barrier free web is a hack.
There is a grey area when you convey meaning with the images. Like the literal and trivial example, if you use an image of text. There are ... "designers" that really do this kind of dumb. And there are other scenarios where the meaning would take up the proverbial thousand words. You just do not pack this into an alt-text.
The screenshot are of Itch game descriptions is a dedicated area. For screenshots. If you want to describe your game with establishing shots, introducing your game characters, you should use the description area and use words in the description, not in some alt-text no one is gonna see these days, since browsers nowadays always load the pictures - the option to not load all pics has been gone for a decade or longer.
Sure it would be nice if the alt-text magically would make visual content accessible, but that is neither it's purpose, nor is this trivially possible. Those establishing shots would still only have alt-text "character shot of the hero". The description should not hide in the alt-text, it should be spelled out for all to read.
And this might be a dumb question, but is there no alt-text possible in the html one uses for a game description? Or is just no one using it?