Re: "website operators should obtain the consent of site visitors before collecting data"
You'll probably find there is a button to turn them all off, however it won't be marked as such. The site you are talking about may have had a button called "measurements" which when clicked killed all the individual providers.
However, this very site probably does not have GDPR compliant cookies in place and the only options for logging out are by going to the individual mentioned sites and trying to work out how to do it from there. They also rely incorrectly on "legitimate business reasons" which, does not actually mean what the companies who rely on it think it means.