Agreed! Nevetheless, in my modest opinion, the easiness of modern notation in LilyPond would be greatly upgraded if one might take the book of Edgard Karkoschka on the XX century notation and check out most common features used by all composers discussed in this very informative book - it will turn out that there are 5-6 such common features (like frame or proportional notation, some few lines and symbols) that might be easily added to the whole pool. In comparison to enormously rich resources devoted in documentation to ancient and medieval notation (circa 100 noteheads only!), it looks like the needs of modern composers are somehow overlooked...