Correct. The two hard problems are sustaining a reaction over a period of time and, given that first constraint, having that reaction generate more collectible energy than is being used to sustain it.
We solved the problem of using fusion to create vast amounts of energy in a short amount of time half a century ago, but the primary application for that approach is excavation (and all ways that word can be applied euphemistically), not energy production.
Indeed, you can build a fusor in your garage that fuses quite happily. The hard part is making a practical power generation system from this. Net energy is very hard.
