I think accessibility is widely misunderstood. The way I view it, it's not only about giving people who need them more ways to access something, but also giving people who want/prefer them those methods as well.
One example of this is wheelchair ramps. Building the ramps benefits those who need them by giving those people a way to go up/down an incline, but many people use the ramps. The ramps are also for those who would prefer to avoid the stairs.
Digital tools are another example of this, and a great one. Keyboard accessibility is a must for people with visual impairments, but also a preference for many who prefer not to move their hand to the mouse constantly. Keyboard-accessible tools are almost always a better experience to all users as a result.
Not building for accessibility is honestly just lazy. It shows that you don't care about your customers, and you don't want them to have a good experience. At best, you want to force your experience on them and only your experience is allowed (my biggest gripe with Apple products honestly).
As for digital art, I've seen a lot of what you mentioned, and I think it's honestly been going on for centuries at this point. It's problematic, especially because not everyone wants to create art in the One True Manner(TM) and may want to experiment with new ways to create art, or may want the art as a part of a larger project and don't really care about the means (as long as it's ethical).
My friend's homophobic dad was diagnosed with HIV right before his wife filed for divorce. They had a long discussion about how he got it, and he admitted to it being another guy. She was very lucky not to have HIV as well.
There does exist a correlation, but like all generalizations, it does not apply to all cases and can come off dismissive, rude, or minimizing when it isn't actually true. I find that it's best to avoid sweeping generalizations for people at all.