Yes but in the real world there are inefficiencies. We can't even transfer energy efficiently enough into the reaction yet to get a net energy gain from the fus

Yes but in the real world there are inefficiencies. We can't even transfer energy efficiently enough into the reaction yet to get a net energy gain from the fusion reaction. And once you reach that milestone, you still have to make transfer of the yield energy into useful work efficient enough to make the whole thing productive. Efficient energy transfer is hard!