Last I checked, the iTunes Store still had music that wasn't on Apple Music. So I take Eddy Cue's claim that Apple Music is superior, like just about everything else the man has said and done, as being totally bunk.
That's a problem with any subscription service (same for Netflix, etc.). Stuff comes and goes, depending on where you live and what arrangements Apple makes with various license holders. Maybe my tastes in music are odd, but it seems too often when I go looking for something, it isn't there. Or, maybe the album is, but a particular track is missing. I guess I've decided I'd just rather get what I want... and can listen to one of a zillion internet radio stations if I just want a mix of 'stuff.'