I think the engineering know-how isn't there as much. When you haven't actually built a plant in 30 years and all the experienced building and designer engineers have moved on, you don't actually know how to build one any more. I feel the delays on the new projects are mostly caused by lack of experience, lack of clarity on actual risks, a lot of second system syndrome (we're doing it right this time, say the maintainer of the previous systems...) and also more regulatory oversight (which is IMO a gold thing). Let's see how these plants built with far more oversight age better than the old ones.

Hungary is just building one right now.

That's great news. I wish the European nuclear industry would have always 10 of these projects running at any time, so we could continuously learn, train and improve ever-so-slightly the designs.