Two things:
DNS blocker apps will not stop this. For example, Google Chrome has Google's own public DNS servers hard-coded in it*, possibly along with its own DNS resolver which bypasses the OS. Soon there will be DNS-over-HTTP(S) which will be pretty much unstoppable. Google may do this under the guise of "helping" a user with bad DNS... or it could be because they're evil and need to DIAF.
Firewall (outbound connection blocker) type apps (like the iOS equivalent of Little Snitch) will not stop this if they become widespread, unless you block all network access. The app maker will simply send all connections back to their servers, then split off the analytics and proxy them to Facebook on the app maker's server side. That is, a connection to required-to-run.suspiciously-cheap-app.com could end up going to Facebook by way of Suspiciously-Cheap-App's server(s). This will continue as long as app developers see a time-savings or monetary advantage in doing so.
To stop this, there should be a simultaneous, possibly-coordinated overreaction by Apple, litigators, and legislators, to make it really clear to all parties--via both civil and criminal mechanisms--that this sort of behavior is not to be tolerated. (Which will never happen.)
*Consider this if you are unfortunate enough to use Google Chrome.