This is fascinating! Can you share more stories?

Not OP, but I’ll throw out that many large commercial websites don’t directly integrate ads themselves. Instead, they use a tag manager.

Often, that tag manager isn’t managed by the technology department, and well-meaning marketing people continue to sign contracts and jam JavaScript into the front end. If there’s also not a good content security policy in place, ad networks quickly become unregulated, all sorts of strange ads come in, and it’s very difficult to control them.

There are a lot of “MarTech” consultants out there that help clients essentially burn their tag manager to the ground, then build it from the ground up to work properly.