And you still need to know how to sing pretty well in tune for any kind of pitch correction software to work. It can sound unnatural if you’re too far out of tune. If you are tone-deaf/too far out of tune, the software won’t work and will sound awful.
Of course that weirdly robotic/T-Pain effect can also be done on purpose as a stylistic choice. Cher, who can obviously sing, first pioneered this stylistic choice on her song “Believe.”
It was mind-blowing at the time.