If I believe I'm going to build a starship in my garage, that makes me delusional. The problem isn't the odds against me being the one person who does this. The problem is that nobody is going to do this, because building a starship in your garage is simply impossible; it's just too hard a job to be done that way.

You assume it is. But maybe you will invent AI and then use it to design a plan of how to build a starship in your garage. So it's not simply impossible. It's just unknown and even if you could theres no reason to believe that would be a good decision. But hey, in a hundred years, who knows what people will build in their garages, or the equivalent of. I immagine people a hundred years ago would believe our projects to be pretty strange.