Does anyone feel in a similar way?
As an analog note note-taker/writer and as an analog reader too (don't underestimate how your ebook reading habits can be also be used/monetized) I can understand how you feel even though I'm not hostile to AI per se: I'm hostile to corporation/privately-owned AI, raiding human knowledge to feed itself and then poo... sell it back to us for a profit, and I'm hostile to AI being sold as the solution to everything.
If I may ask , don't you think there is a higher risk using Substack, than some website/blog you would fully control and own, to see your content being force fed to AI without yout consent? I mean, like it happened with reddit, right?