They already have that part figured out. From the article:
> When we encountered a similar problem last year, we found a simple solution: block the undesired traffic from these apps. Even so, we continue to serve about 100TB of “Access Denied” pages monthly!
The difference is that serving Access Denied Leads to the users of these malicious browsers just getting more ads over time, as the filter lists can’t be updated anymore. Serving a special list containing popular sites would result in the users almost instantly not being able anymore to access these popular sites, resulting in requests to the developers to fix their shitty browser or switching altogether.