In fact, it is sometimes entertaining to imagine that somewhere in the depths of the GNOME cult compound, they keep a single individual, who is legally blind, physically incapable of using a keyboard, simultaneously belongs to all demographic groups that are traditionally underrepresented among computer users, and has in fact never used a computer themselves but was shown a few things on an iPhone by their Gen Alpha great grandnephew. All these factors combine to turn this person (affectionately referred to as Mother Gnome by those in the know) into a utility monster of UI design, so that it becomes an absolute moral imperative to design things to appeal to them, at whatever expense it takes.
But GNOME team did say they have done tons of ux studies long after SUN.
Accessibility is about making the UI usable for everyone - that happens to include handicapped people (who often do require specific accommodations, such as reduced animations, TTS, zoom, color filters...), but that also includes power users (who e.g. need to do some specific task often enough, that they might benefit from the UI being scriptable), people who sometimes need to use a computer late at night (automatic dark mode), people who need to stay focused on a specific set of tasks (do not disturb with per-app notification filtering that syncs across devices), etc etc etc.
It's this "oh it's for the handicapped" mindset that makes UIs unusable for everyone.