That turns out to not be true, at least not with the tokamak reactors most groups are pursuing.

You see, at some point you need a shield around the reactor to actually absorb all the high energy particles released, and turn that energy into heat. That's the whole point of the reactor, to generate heat and run a turbine. You absorb those high energy particles with a "blanket", that's just what they call the shield around the reactor.

Here's the issue, absorbing all those high energy particles necessarily results in transmuting the material absorbing them. That blanket becomes brittle and eventually needs to be replaced. Not coincidentally, that blanket is also now radioactive, because you've bombarded it with protons and neutrons and it's now partially made up of unstable, radioactive elements.

So while fission reactors have radioactive fuel rods to dispose of, fusion reactors will have radioactive blankets to dispose of. Who knows if this is an improvement.