The poetry of music, Copland intimates, is composed both by the musician, in the creation of music and its interpretation in performance, and by the listener, in the act of listening that is itself the work of reflective interpretation. This makes listening as much a creative act as composition and performance — not a passive receptivity to the object that is music, but an active practice that confers upon the object its meaning: an art to be mastered, a talent to be honed.
Whilst Feature Parity often sounds like a reasonable proposition, we have learnt the hard way that people greatly underestimate the effort required, and thus misjudge the choice between this and the other alternatives. For example even just defining the 'as is' scope can be a huge effort, especially for legacy systems that have become core to the business.
Most legacy systems have 'bloated' over time, with many features unused by users (50% according to a 2014 Standish Group report) as new features have been added without the old ones being removed. Workarounds for past bugs and limitations have become 'must have' requirements for current business processes, with the way users work defined as much by the limitations of legacy as anything else. Rebuilding these features is not only waste it also represents a missed opportunity to build what is actually needed today. These systems were often defined 10 or 20 years ago within the constraints of previous generations of technology, it very rarely makes sense to replicate them 'as is'.