Fascinating - I find the opposite is true. I think of edge cases more and direct the exploration of them. I’ve found my 35 years experience tells me where the gaps will be and I’m usually right. I’ve been able to build much more complex software than before not because I didn’t know how but because as one person I couldn’t possibly do it. The process isn’t any easier just faster.
I’ve found also AI assisted stuff is remarkable for algorithmically complex things to implement.
However one thing I definitely identify with is the trouble sleeping. I am finally able to do a plethora of things I couldn’t do before due to the limits of one man typing. But I don’t build tools I don’t need, I have too little time and too many needs.
If you’ve worked on a code base built by more than you, you don’t understand and you don’t have control. Part of being an experienced engineer is understanding how to deal with that effectively at scale.