The breeder part is the production of U-233 (which is then fissioned and used to provide the neutrons for converting Th-232 into U-233 (with a chemical separation and decay storage step in between)) which although has a tight neutron economy is viable.
Working reactors for such designs were funded by the US airforce and they did operate as expected.
If you wish to argue that one will need U-235 as a startup fuel or that there are technical problems in large scale energy production it is not yet able to address, I would definitely agree on that; the technology needs more research before we depend upon it and that Uranium light water reactors are likely to be the running standard until such time and needed investment occurs. But we have enough U-235 in nuclear waste stockpiles to fuel our civilization for a thousand years to work out the details.