I'm afraid this bit - ROI time / profitability - is what will kill practical applicability of fusion power. There's already tens if not hundreds of billions in

I'm afraid this bit - ROI time / profitability - is what will kill practical applicability of fusion power. There's already tens if not hundreds of billions in investments and decades of research, and it will take that again to turn it into a commercial endeavour, if ever. That said, nuclear is great for baseline power production, and even with renewables generating the brunt of electricity, you still need a baseline and a quickly scaling backup (gas generators). Battery parks help too for those, but they have limited capacity of course.