I'm also writing a novel, and using text to speech to hear how it sounds. One of the ones built into Mac OS. And I'd agree with your assessment, I value the synthesiser for bringing my attention to things my eyes gloss over, such as unnecessary repetition and typos which are still correctly spelled words (a common one for me is lose/loose).

But: AI was seen as "decades" away from beating humans at go, even 6 months before it did.

I don't know how far we are from them writing award winning novels (awards we care about, it doesn't count if it's an award for best AI), though my gut feeling is we need another breakthrough as significant as the transformer model… but even then, that's only a 1σ feeling.