Actually you dont need to trust a upstream DNS server. Checkout dnscrypt-proxy in github. You can use dnscrypt with Anonymized DNS relays. You can use the IP of this dnscrypt-proxy as your DNS resolver.
Its a nice idea , but I will hate the way these tech giants choose to implement it. 99% of implementation would need location to be tracked 24x7 and stored in their server . If someone would have a local or private way to do this , I’m exited.
Its their platform . its their choice. We don’t have a choice to force them to allow adblockers. There is always a choice to load content after the ads are served . If they go that route then no adblocker can bypass it.