I feel like both of you are correct. It feels to me that Spotify's recommendations easily gets stuck in a 'local maxima' where it just keeps recommending the same music over again with little variation. I found much more variation from other music streaming services where the playlists are supposedly actually human curated. Music just ends up feeling a lot more bland with Spotify, in my experience.
I don't even know what the Discover Weekly playlist is supposed to be. It frequently puts in not-new songs from not-new artists Spotify know I've been listening to.