The problem is that by the 80s and 90s we were trying to wind down production of nuclear weapons as the cold war was winding down. Some of these reprocessing methods, like in France, reprocess the plutonium, and modern reactors just don't produce plutonium anymore. Also, some of the methods create uranium that is enriched to as much as 20%. With terrorism a big concern, that would be a pretty tempting target.

That being said, we are developing the tech, just very, very slowly. And now that renewables are cheap, it's just not necessary to have so many fueled generators. So the long term profit just isn't there for companies to want to invest. The area where I live is primarily hydro power, which is one of the more predictable renewables. But offshore wind farms give a pretty steady flow as well. And in deserts concentrated solar power can generate enough energy during the peak times when A/C is being used. And if there were better battery tech, more could be stored for use at night than currently is, and wind is still pretty reliable due to the changes in temperature from day to night.

Of course we still need fueled generators, but we shouldn't be expanding them, we should be concentrating on using them only as a backup to renewables.