Curious comments , you have to be a bit more specific as to where and when it was and was was unsafe in your eyes. . In Cruise in Upper airspace the controller anywhere does not have to read back anything. If it is extremely busy he/she will only acknowledge the call, not the contents.
As to not picking up the incorrect read backs, it is definitively not a policy anywhere, but as some of us have Mode S downlink of your aircraft parameters, and those are more relevant , a bad habit of not concentrating on R/T readbacks but what you actually see selected in the FD might be starting here. Not good. Lastly one comment you made would indicate a call sign confusion, yes. that is still a real and serious issue. and valid for everyone, pilots too....