Copying and distributing works isn’t identical to theft (deliberately depriving someone of their property), but you’re enjoying someone’s work without compensating them, so it isn’t totally unlike depriving them of something.
I guess it depends how you feel about refusing to pay a window washer. Or indeed you not being paid by your employer. It isn’t theft, but someone is clearly stiffing someone else.
As for only big companies benefitting from the copyright regime… seems like an ideological assumption. I know plenty of authors and they are quite happy having legal protections around their work which means they can earn from their labour.