It causes genuine harm, I'm visually impaired and I've wandered into construction zones because advertising billboards are mounted near and "road work ahead" signs and everything is all just bright and bold.

I don't know what's official, everything is competing for my attention but I have very little capacity to dedicate my full attention to a visual sign. The end result is incredibly fatiguing, seeing a bright sign and straining to ensure I read it because it's colours look important, nope, it's an ad, that was a waste of energy, oh look another one with the same blurry colours and type setting it's probably the same ad.... Nope that one actually needed my attention, and now I'm somewhere I shouldn't be and I'm in danger.

I'm also hard of hearing, but fortunately audio adber in the public isn't as bad, but anyone who's hearing impaired knows how fatiguing it is to try and filter through noise. It's the exact same for visual impairment.