ITER is a dead end. It would require multiple miracles to get anything remotely competitive out of it, and that's just not going to happen.

First, realize what's holding back nuclear fission. It's not nuclear waste, or safety, or Greenpeace, or the cost of uranium. It's the capital cost of the powerplants, and to a lesser extent the non-fuel operating cost of the plants.

Fusion would make these two main problems worse, not better.

The fusion power density of ITER's plasma (note: just the plasma, not including the total volume of the reactor) is 0.6 MW/m^3. The power density of the core of a pressurized water reactor, on the other hand, is 100 MW/m^3. And the machinery around a PWR core is much simpler than all the magnets and such around a fusion core.

(The ARC reactor has somewhat higher power density, but still sucks compared to a PWR.)

That fusion power density sucks has been known for decades. It follows from basic physical considerations (square-cube law) and is largely independent of the details of the reactor design. See Lawrence Lidsky's famous 1983 article in MIT's Technology Review, "The Trouble With Fusion".

The inevitable result of this is that fusion power will be more expensive than fission power. The capital cost will be much higher.

ITER's high cost has been explained as due to international coordination, but actually the cost was lowballed from the start. If they had gone with cost estimates of previous reactors, and scaled them on the cost/size plot, ITER should have been estimated at 3-4x what they said it would cost.

Now, operating cost...

Fusion reactors are extremely complex, much more so than fission reactors. This means they will break more often. And all the parts inboard of a DT (or DD, or D3He) reactor's biological shield (in ARC, this includes the magnets) will be too hot for hands-on maintenance. So all the repairs will have to be done by robots. Good luck with that!

In a reactor the size of ITER, all the armor on the first wall will have to be water cooled. Each component slab of this armor cannot fail. A single leak in any of them will render the reactor incapable of sustaining a plasma. I understand that when conventional reliability estimation techniques are applied to these things, one concludes the reactor will be able to operate only a few percent of the time. This isn't even good enough for a research reactor, never mind a commercial reactor.

And what will fusion face if, by some miracle, a "working" reactor is finally made? In the last 40 years photovoltaic modules have declined in cost by about a factor of 200. What will happen in the next 40 years? ITER, if all its fusion output were converted to electrical power at 40% efficiency (and none needed to be fed back) would cost > $100/W. PV modules are now about a factor o 300x less than that. Even if we divide the PV number by four, ITER is so far out of the running it's absurd.

To finish, I'll add that to truly replace fossil fuels, electrical power has to come in cheap enough that resistive heat displaces natural gas. This requires electricity around $0.01/kWh. There appears to be no chance ITER, ARC, or any of the other fusion schemes could approach this, even with hugely optimistic assumptions.