Music royalties are also set by a panel of judges (Copyright Royalty Board). Spotify is not legally able to "screw" anyone. Their pro rata model pays as much or more than the legal requirement. The economics of radio and internet streaming, especially in a world with a democratic explosion of access to recording technology, simply aren't conducive to recording being lucrative.
Record labels are in the business of screwing musicians, though.
1) Using legally required minimum as floor is malicious, this is US we're talking about 2) CRB's ruling is very new and you want us to forget how Spotify was screwing everybody over all preceding years 3) the rates from CRB are based on total revenue of the streaming service which leaves a LOT up for manipulation if the company wants to pay less. Read what real bands and musicians say about how much they get paid from Spotify and others
Record labels are in the business of screwing musicians, though.