A glass-half-empty view of that would be that there isn't a single reason which could be fixed to avoid all future issues. Fukushima AFAIK didn't have the design and operational mistakes which led to the Chernobyl incident, but that wasn't enough to prevent it from having its own incident. Which other causes we might be missing which could lead to new severe incidents in other nuclear power plants?

(And, by the way, the bad part IMO was not "both were meltdowns", but "both were explosions"; if it were just the meltdown, it would stay confined within the power plant, while the explosions are what spread the damage. Yes, they weren't nuclear explosions, but even a non-nuclear explosion in a nuclear power plant is bad.)

Humans.

You mention both Cost Savings and Design Mistakes. Those are common, and will occur in future projects.

Don't think totalitarian Gov has any monopoly on hiding design problems. Every company does it.

Those are both things, drives, that the US has shown to be incapable of administering. All industry is rife with cost cutting. And "safety" is very much cut in the name of profits. It happens today, just not 'obvious'. We don't hear about it until there is a meltdown.

I do hope that new designs are better. But I am absolutely not confident that humans have learned anything and wont subvert any improved designs again for cost savings.

This sounds exactly like what could happen when a private for-profit company would exploit nuclear, which is already happening