I agree it's a game changer in the long term (eg for multiplanetary life), but in the timeframe that we have to do something about climate change (rather short)

I agree it's a game changer in the long term (eg for multiplanetary life), but in the timeframe that we have to do something about climate change (rather short), the effect of fusion depends hugely on the cost of building and running a fusion plant. If it is more expensive per Watt than a solar panel and a battery, not much is gained. If it is much cheaper, then it will indeed be a game changer in the short term. But currently it doesn't really look like it will be super cheap when it becomes available.