Another class of instruments that has evolved in all of the ways you named is the synthesizer. Certainly vocal performance is a very old tradition but to write off synth vocals as superficial is in my opinion throwing the baby out with the bath water. Sound synthesis has gone from an experimental and avant-garde playground to one of the most expressive and versatile fields of music composition.

Techniques like additive, FM, and physical modeling synthesis have opened up whole new worlds of musical possibilities to explore. The combination of synths with vocals only widens the expressivity, range, color, and ultimately individualism that voice alone can accomplish. For every autotuned vocal track in bad taste there are just as many creative uses of vocoders, talk boxes, filters and samplers that enhance creative expression.