For typical single-based pop/top-40 that could be true. But for the long tail of most album-oriented music (including the fairly obscure stuff I listen to), it

For typical single-based pop/top-40 that could be true. But for the long tail of most album-oriented music (including the fairly obscure stuff I listen to), its the producer and musician(s) working together to create a coherent artistic work. Obviously that doesn't always result in an album of consistently great songs, but in my experience as as an occasional musician, recording engineer, and producer, there's always more material than will fit on the album. Part of the creative process is to build that into a form that best expresses the concept of the work as a whole. That usually involves selection & curation, not adding extra filling. My opinion, of course.