I think the "appification of the web", where information is increasingly presented in a custom UI that is supposed to resemble a desktop application, is largely to blame for that, along with the tendency to emphasise form over function (although this is not restricted to the web, it seems to happen whenever people whose only job is to design, and not also create content as well, is present) since there's a general perception that the more "designed" (with graphical elements that are not necessarily useful, distracting animations, multicoloured things whose only purpose is to be attention-getting, etc.) a webpage the better it is. The effect is to emphasise presentation over content, which doesn't please those who are more interested in the latter and certainly isn't any better for accessibility. The overuse of and reliance on Javascript doesn't help matters either. In fact I'd say the web has become less accessible now as compared to e.g. 20 years ago.

In Firefox, when I find a page that is beautifully inaccessible:

View/Page Style/No Style

which gives me beautiful, high contrast black on white, and text that flows fully within the borders of the browser without having to scroll sideways.