I can’t accurately estimate non-trivial software. I’ve never met anybody who can accurately estimate non-trivial software. I’ve never seen anybody claim to be able to accurately estimate non-trivial software. Yet for some reason people still insist that estimating non-trivial software is not only possible, but trivial.
I think the real reason estimations are hard is that basically every developer is working on projects too hard for them. Like, if you are so good at your current job that you can reliably churn out good solutions with ease then instead of just producing you would move on to do harder things for better pay.