I'm hopeful for fusion too, but I don't think it's viable under capitalism.

The problem with (fission) nuclear power is that, with for-profit companies financing power plants by mortgages, which is what we have, it takes so long to build the plant that the mortgage has accumulated so much interest that it'll take forever to pay off. So even though they're more profitable than a gas powered plant once completed, that extra profit is going towards paying off a huge mortgage for a very long time, before finally actually paying off.

By any reasonable future forecast, a fusion power plant is going to be an even larger up front cost than a fission one, so it just can't work without state planning.

You can see a big difference with solar though, which absolutely does not have this problem. Setting up a new solar plant is fast and cheap now, and now that it's cheap, companies and countries are itching to get in on it. But of course there are oil lobbyists and anti-environmental death cultists in the way of that. But they're actively fighting against what'd be more profitable, so even under capitalism, there's only so long until solar power wins.

(But the timeline for solar power winning under capitalism still sucks and anything that averts climate change faster is better.)

We should definitely keep earnestly working on fusion, because the potential is so great, and the fundamental physics are sound (after all, solar is just harvesting the waste energy of fusion). But there is a high likelihood that it will not be ready soon, or ever, and so we have to plan as if we won't have access to it in time.