Apple Music reached 10m paid subscribers in 6 months it took Spotify 6 years to reach that number... so no it hasn't flopped. Also wait till spotify has to discontinue its free tier
Of course it's not as big as Spotify yet, but it's been half a year and it's already at half of Spotify's 20M subscribers (which took 3+ years to get).
It's great but it ****ed my library. They replaced some studio tracks with live versions and etc. it messed up my artwork too. But iCloud library saves a ton of space and downloading HD without having to sync is lit.