> The most common refrain is that popstars often write their music. This is misleading: they write the lyrics, suggest a general vibe, and some rough melodies or chords. And even this is a stretch many times. They are not composing or producing the music in any larger sense, and this is the pivotal part of actually making music.

To be fair, if they write the lyrics, define the vibe/feel of the song, and compose the melody and chord progression, then that does sound like the vast majority of the song. What's left - I guess some additional instrumentation, the percussion, production? To me it does sound fair to credit the popstar with having composed the music in this case.