You're claiming radio didn't really affect discovery, when radio music discovery was being regulated by federal law and driving congressional hearings by the 1950s.
Radio changed music as much as streaming did, and before streaming, MTV did too.
I'm saying that radio isn't good for discovery, precisely because its selection is so narrow compared to an on-demand catalog of algorithmically selected music that Spotify provides.
Radio changed music as much as streaming did, and before streaming, MTV did too.