Copying someone’s copywritten work is IP theft
Says who?
Every law on the subject deals with "infringement", not "theft".
Copyright is a state-mandated monopoly on reproducing a specific creative work. Violating the state's rules about that monopoly is not "theft".
To actually have IP theft, you'd have to use some nefarious means to acquire ownership of the IP, taking it away from the artist.
If your friend made an artwork, but before they published it, you took it to the copyright office and had the copyright registered in your name ... now that would be IP "theft". You actually stole the IP from someone and deprived them of that IP by doing so.