I'd love to see viable nuclear fusion power, but the lack of more investment at the moment doesn't really seem unreasonable. As you said, there are a number of other green alternatives, including traditional nuclear fission power, that have proven they can be real alternatives to fossil fuels and that would benefit from continued investment.
Unless I've missed something, nuclear fusion meanwhile has yet to demonstrate realistic commercial power generation, even as a proof of concept or a complete path to get to that point. In other words, more research is definitely worthwhile, but it also seems possible it will be a dead end at least in the near term. It's hard to argue prioritizing that over other things that have been generating real commercial power for decades. I'm all in favor of an all-of-the-above approach, but prioritization almost always has to be the reality.