On https://orgmode.tecosaur.com/features.html:

The first figure is not labeled, so I do not know what it is. The second figure is just labeled "babel.gif", which doesn't tell me much (pretending to be some one who knows nothing of Org-mode). After the "Collapsable Editing" heading, that figure is labeled "folding.gif" which is slightly better, but could be described much more, and without the .gif extension in the alt-text.

After the "Task Management" heading, this figure likewise isn't described, only having its file name, "planning.gif", as the alt-text or description. After the "tables" heading, the figure, tables.gif, should be described using Alt-text instead of just leaving the file name there.

After the "publishing" heading, the "exports.gif" figure should be described. Also after that heading, in the list of export formats, the second item just says "clickable" as the list item.

After the "Extensibility" heading, the figure does not even have a file name as its Alt-text. After the "Time Tracking (Clocking)", the figure has no Alt-text. After the "Agendas" heading, the figure has no Alt-text.

After the "Capturing" heading, the figure only has "capturing.gif" as the Alt-text. After the "With your mobile phone" heading, the figure below has "beorg.png" as the Alt-text.

Also, I cannot find the area to view the Org-mode source of a page. Basically, describe the figures, don't just leave the description as the file name. I tested this with Google Chrome 85, and the NVDA screen reader. The rest of the site looks good.