Fusion milestones have been newly achieved in the past 10 years. You may be right that it'll remain "50 years away" for generations still, but it's not evident to me that this will be the case. We barely had fission energy stable 60 years ago, we now know a lot more about the requirements and limitations for fusion, and we're allegedly still saying 50 years? That's a lot more reliable, and note that n=2 here (a bit more than one set of fifty years having gone by, a second fifty being underway and it still seeming like that). If it were "always 10 years away" since the 50s, that'd be quite a different story.