If we stopped what we worked on every time some nice theory came around which could work "better" (for whatever definition of better) we would never get anythin

If we stopped what we worked on every time some nice theory came around which could work "better" (for whatever definition of better) we would never get anything done. Scientists/companies working in these areas are free to produce results that make ITER obsolete. After they've done that we can discuss about abandoning the - from our current understanding of science - most likely path to (more or less) unlimited energy. So far, they are not further along than let's say fusion experiments in 1960.