Most marketers should know exactly how effective their ads are by measuring to the end of the funnel. This is standard for most business and while bots are a problem, if you're judging online advertising at the front end of the funnel that's to a large part on them for a bad setup and/or optimisation.
Maybe this is a cynical take, but, if they get to the bottom of things, and show their boss/client that the ad-spend is not returning so much, it seems it would portend bad things for the marketer.
I really don't know, and it seems like a very hard problem.
Maybe this is the time for that Upton Sinclair quote: "It is difficult to get a man to understand something, when his salary depends upon his not understanding it,"