From the OP: > declining concern for the future in comparison to the present Breaking backwards compatibility has a larger negative impact in the _present_ th

From the OP: > declining concern for the future in comparison to the present Breaking backwards compatibility has a larger negative impact in the _present_ than the cruft of old APIs and code. But that impact is temporary. However, the negative impacts of cruft can have a larger impact _in total_ over the entire lifetime of the operating system.