There's no guarantee that any of the technology tree branches have profitable fusion power in them. I'm reasonably confident that controlled fusion with net energy gain is technologically possible. Determining whether it can be profitable is a lot harder. Profitability depends on what every other competitor can do, as well as what your own technology can do. That's why extremely well-proven technologies like coal-fired electrical generators can become unprofitable when competing technologies improve.

If there were a global carbon tax, it would give fusion an advantage against fossil fuels, but that would also be to the advantage of fission and renewables. In the absence of a global carbon tax, is fusion going to be cheap enough to displace fossil fueled power? We've had the technology for emissions-free electricity for decades, but it's difficult to profitably compete with fossil-based generators enjoying unpriced externalities.