Fusion _might_ become that cheap non polluting source, but right now we don't know. What we do know is: renewables are cheap right now.
Now applied to hydrogen, we can even say that hydrogen production can perfectly adapt to the intermittency of renewables. But I'm of the opinion that we need to decarbonate our grids further before we start looking into using renewables for h2 production.
Usable Earth based Fusion is still quite some time away, meanwhile the immediate issue of mitigating fossil fuel byproducts is pressing.
Coal and nuclear are uncompetitive simply from the cost of the steam side. Today you can just about give a steam plant free energy and it still makes a loss.
Solar or wind does not have this limitation. CCGT gas plants gets around it by having a turbine giving raw mechanical power and then utilizing the same awful steam side to get the last percentage points of efficiency at a much smaller required scale.
Unless you can step around the steam turbine I am not so positive on fusions future outside of incredibly small niches.