This points out the foolishness of having reactors that are inherently unstable when stable ones are available.
Perhaps I misunderstand this remark, but if I interpret it in a straightforward manner that better reactor designs are now available...
Nuclear reactors are expensive to build. The costs are amortized over the expected lifetime of the reactor. Investment is upfront, and payback is deferred (as in deferred gratification). Do you go out and buy a new cell phone every month because your current cellphone has been rendered obsolete by the latest model? Probably not, if you signed a 2 year contract. Similarly with nuclear reactors, only there is several years of studies, permits, regulations, and change orders to deal with. Not to mention tree huggers, pandering politicians, and a population who knows nothing more about energy than how to look for the nearest wall outlet.