Re:many users don't know about \shape

[Kevin Patrick Barry]

Or the post processing would have been done using inkscape or some
similar tool...  At any rate, \shape is no substitute to fixing
LilyPond's typesetting of slurs.  It's a stop-gap measure tied into a
particular version of LilyPond and loosely tied into a particular
version of a score.  Which may sometimes cause less work than fixups
firmly tied into a particular printing of the score (which Inkscape
touchup work is).  But it is still something you can't depend on.

I think music notation is such that people are always going to need the ability to change the shape of slurs.  Before discovering \shape I used to manually tweak control points to get what I wanted, which is a long and torturous process.  If someone were to take \shape away in a future version of LilyPond (this implication is in your post, even if unintended) I would almost certainly not upgrade, even if significant improvements were made to LilyPond's slurs.  I don't mean this as a slight on LilyPond's slurs, which are beautiful for the most part, just that people are always going to need to be able to change them.

Kevin