That's part of the problem with fairly basic research like what we're putting into fusion. Without making the investment, doing the science and engineering to actually study these things and learn how they work and how we can do them better, we won't know how or whether they can be made cheaper, miniaturized, etc.

This isn't the same kind of problem that most of us are used to dealing with in our daily lives—where the fundamental components, and the fundamental science, that make it all up are well-understood and fairly mature, and what we have to do is come up with creative ways to apply it. This is the kind of "we don't know if any specific avenue of research will ever pay back a positive monetary ROI, but pursuing them is important anyway" science that we need to be doing with or without fusion as a specific goal, because over time, it will produce years or decades of silence, punctuated by small, incremental improvements in our understanding of the universe...and then an amazing breakthrough like practical, commercially-viable fusion power.

But only if we are willing to patiently fund it through those years or decades of boring stuff.