Building new reactors is costly and you need public opinion to agree to that. Unfortunately when someone proposes building new kinds of reactors some asshole backed by "Oil Corp Co." runs ahead screaming "Chernobyl Fukushima!!!" and public opinion is instantly biased negatively to that idea.

Its completely illogical to block Nuclear Power advancement, but goverments are either lobbed or public opinion disagrees after being fed complete horseshit disinformation.

Fast breeder reactors that have been successfully run are difficult/costly and have proliferation concerns.

They’re, arguably, the only country left with a serious nuclear industry. One that can propose a new reactor design and follow up to commercialization.

The US’ got lazy, the European was good, but never innovative, Canada and S. Africa are too small.

The US didn't get lazy, the US allowed the market to speak (with substantial deregulation of the electrical power generation industry). And the market said nuclear is a loser technology, compared to alternatives. Not investing in loser technologies is not laziness, but intelligence.