Well of the fonts listed, 2 out of the 3 would also prevent any human from wanting to read it and the third becomes an ineffective counter measure if it's widely used.
I think the line of reasoning that a method should provide as much accessibility as possible to not alienate real humans is a good one. You use 'have to' as if there aren't better solutions that could be invented, but such will only occur if we challenge the imperfect solutions we have now.
I don’t understand how you think a font would block a bot from reading your blog in the first place?
It’s not even going to render the damn website. If it decides to and detects your retarded font it could just change the font trivially. You’d have to fundamentally fuck up the html text content for it to work at all, and then all you’ll do is inconvenience real people that you’d be extremely lucky to have attracted to your blog in the first place.
If I have to block a blind person from reading my blog to block an AI from training on it, I'll make that trade every time.