Fusion turns out to be a LOT harder than anybody thought. Physicists have been saying it is 10 years away for 50+ years, now. Tokamak looked promising until you understand the surface area to volume relationship, then it becomes obvious you can't have a thread of plasma many meters long at 10 megaKelvins, all the heat leaks away.
The only hope is a VERY compact plasma, and that is a hard state to maintain. And, the implosion devices are most likely to self destruct due to the massive thermal cycling. Not immediately, but it seems like they would end up requiring huge amounts of maintenance.
Jon