I would hope all our web designer/developer spidey senses trigger when the solution to an accessibility problem isn’t “fix the issue” but rather “add extra stuff to the page.” This Overlay Fact Sheet website explains that. An “Overlay” is one of those “add extra stuff to the page” things, ostensibly for improving accessibility. Except, even though marketing may suggest they are a silver bullet to accessibility, they are… not.
The site does a much better job laying that out than I can, so go check it out. As I write, it’s signed by 352 people, mostly people who are accessibility professionals.