Not every response to capitalisms is socialism. Street gangs are not socialists when they wave shop lift, or recycle man hole covers, they are criminal. File Sharing is about the same but for most the crime was not considered a crime as mix tape was never really thought of as a crime. Sometimes people give the middle finger to the state, whatever the economic theory is of the regulatory state.
If by “mix tape” you mean downloading and making a copy of music, then, yes, it was most certainly thought a crime. Since it was and is. If we are talking about commercially created music it is copyrighted when created, by the musician. He, in order to make money, gives his right to some outfit. That music is still copyrighted and owned only by that outfit. Yes, the usual defense was: “This is not theft since the owner still has his copy.” Slimy defense since making extra copies dilutes the market — stealing profit from the organization. In previous career doing deals with any Chinese company was always a problem since the CCP does not recognize copyright since communism does not recognize private property. Same mechanism operating here.