Since there are a handful (maybe dozens) of companies who implement this popup feature as a service (e.g. CookieYes), a browser plugin to automate the "no to all" could be handy. That is, the plugin would know the provider and navigate the labyrinth of settings to disable all of them.
And then a handful of companies can offer a service to let advertisers punch through the plugins. And then another plugin could block that!
Thing is you’re probably right. The modern web is made of middlemen inserting themselves into user experiences to divert and extract revenue from the primary stream between consumer and producer. There’s always room for another layer.
That's not always enough, sometimes you need some code simulating the "deny all" clicks or tweaking CSS class lists on the body and html elements.
Otherwise, you might end up with some unscrollable page because for instance there's a CSS rule that blocks scrolling when the modal is there and restores it when the modal closes and this handling is unfortunately done in JS.
