It was, on a technical level, the most interesting work I’ve ever done. What people say about the US government being ahead of the commercially available technology curve is certainly true.

The work I did absolutely had positive impact on the world.

People rush to criticize and write off working in the defense sector, but it can be a very rewarding place to work. There are absolutely problems in that sector - bad management and regulatory capture being primary among them. (Ultimately, those are why I left.)

It’s hard to judge accurately from the outside. That’s the nature of classified work: by definition, you can’t know what you’re getting yourself into until you’ve jumped with both feet.