I could also interpret that saying as "Don't opt for the company whose only business is music streaming, when Apple has more than enough resources to sustain Apple Music for however long it takes to be successful."There's and old saying: "Don't put all your eggs in one basket."
If I were in the market for streaming music, and I'm not, I would go with Spotify instead of Apple Music. This is also the reason I don't use iCloud.

Though honestly, I don't see why it's a bad thing to go all in on the Apple ecosystem. Switching costs aside, Apple Music does benefit from Siri integration and is available on the Apple TV. I do use iCloud for certain purposes, but not exclusively.
Apple's services might not be the best "in-class", but their tight integration can give them an edge over the rest of the competition. I am actually looking at how I can further wean myself off Google and embrace the Apple ecosystem in its entirety.
