Imagine you were making a visual novel:
https://en.wikipedia.org/wiki/Visual_novel
you could write one is not voiced, voiced with some exclamations ("Are you sure that's safe?" gets replaced with "Yikes!") voiced in some places and not voiced in others, or fully voiced.
In 2020 you need to hire and direct a voice actor because TTS is nowhere near good enough. If there was a good enough TTS you wouldn't need to hire the voice actor although you'd still need to direct the TTS.
Two of my favorite speakers are Lester Holt and Tanaka Rie and I'd like to see a computer voice that approaches that kind of person.
