If something takes a long time to pay off, it may or may not be worth doing....perhaps the money could have been better spent investing in an alternative technology that will pay off sooner. No one has the answer or knows what is the right course of action to yield the best long-term results.
That's just logically fallacious, by pure definition of terms. If it pays off, it's worth doing. You would see the benefits of solar panels on your roof, I would see the benefits of solar panels on my room, my neighbor would see the benefits of solar panels on my roof, a guy across my state would notice benefits from solar panels on my roof. You want a shorter term pay off? Go get a loan for geo-thermal energy, depending upon your house, you'll save money this exact month, and in a few years when that loan is paid off, you'll be saving a ton of money. If you think that somehow, an investment that takes ten years to start paying off is a malinvestment, you're just being completely short sighted. This isn't some mysterious field of technology, it is something easily understandable, it's basically just math. The best long-term results, period, involved being more efficient now, and the sooner you can be more efficient, the better. Period. You know what does not lead to the best long-term results? Continuing to use the outdated, inefficient, dirty and polluting form of energy we have right now.
You're making an argument that since the market hasn't done it yet, it's not effective, or efficient. That is just fucking false on every level, on every logical level, and shows just how reliant you are upon this one idea of the market being the answer to everything.