"Old" as in "we built it and discovered it's not wanted". The French basically gave up on the idea of fast reactors (as did the Japanese, although their fast reactor program appears to have been an excuse to obtain a stockpile of separated plutonium in case they need to make bombs). There's no market for them. The Russians have continued to try, but they're selling LWRs.
The big problem with fission is that it's too expensive. Fast reactors make that main problem worse. There is no economic margin to do fancy (and expensive) things to try to address the lesser issue of nuclear waste.
In an economic sense, when compared to burner reactors, this is correct. As the rise of wind and solar has shown however, political will and popularity matter more than pure economics. Burner reactors are more of a 22nd century technology, assuming the grid storage problem doesn’t get solved by then and we just go full renewable on economics. But nothing is set in stone
What nonsense. What solar and wind have shown is the overwhelming importance of economics. They are dominating now because they have become cheap, not because of some sort of "triumph of the will". And they have become cheap because they are inherently the kind of technologies that has good experience curves. Unlike nuclear.
Nonsense? Why was US nuclear built at all in the 60’s and 70’s? Or in France? Because it was cheaper? No. It was built because people thought it was a good idea. The same is true for intermittents today. They are popular with a section of the population so they get the funding. And no, nuclear has fantastic experience curves. Look at any country building lots of reactors and the n-th of a kind is cheap. Building out nuclear and maintaining industry experience works to keep costs low.
The big problem with fission is that it's too expensive. Fast reactors make that main problem worse. There is no economic margin to do fancy (and expensive) things to try to address the lesser issue of nuclear waste.