I have a particular interest in early Mormon history and the history of the western US, and there are some really great books that aren't available as audio. I ended up generating some with aws and while the voice annoyed me, I was willing to do it, and the cost was much higher than a normal audiobook would cost.
I think in reality, the more popular books will get a pro reading, but as long as it's labeled, there will be a market for ai audiobooks.
This reminds me of the “I’ll never listen to mp3, I love my <whatever>.” The goal wasn’t to convince existing people but to expand to new people.
https://www.drabblecast.org/2007/12/20/drabblecast-43-jelly-...
Warning: the above has mild language and adult themes.
https://www.drabblecast.org/2010/07/27/drabblecast-173-go-be...
If I want mediocre text to speech, I have that on my Kindle.