Your totally right! People don’t realize there is so much technical stuff going on in a song nowadays. They literally think anything and everything is autotune lol. Doubling/Layering is probably one of the best effects used on vocals. Simply doubling your main vocal sounds amazing and unlike any other effect. Pitch is only a small part of a vocal recording in the bigger picture. The average person can’t begin to comprehend how intricate a producers vocal chain is. It’s not just slap Autotune on and done. There’s is so much more to it in the producing and engineering. And your also completely right with the autotune being more audible when the vocalist was more off to begin with. Autotune is literally snapping notes to their correct spots on a grid. The more in tune you are the less you hear it working. And your right it doesn’t mean your bad at singing, like I said pitch is a small part of singing that can be fixed. The most important thing is probably going to be your unique tone or sound. You CANNOT, contrary to popular belief, manufacture something like that.