I would actually think the smaller ones would detect the issue faster, simply because they would see ad clicks and recognize no new business, as opposed to bigger ones, that this would be an insignificant change they wouldn't notice.
In addition, I don't see the companies paying for ads getting hurt the most, in the end, if they would recognize that these types of ads are inefficient, they just wouldn't use it as much (they would use other outlets) or lower how much the value (and pay) for it. Which would help me (by getting rid of something I dislike), and at the same time hurt those that maintain and support that part of the business in the adtech world (another plus for me).