The reasons further down explain why utilities are very slow to react and why even after a better choice is available. But even with your further comparison, y

The reasons further down explain why utilities are very slow to react and why even after a better choice is available. But even with your further comparison, you are falling prey to the same bad logic: solar can't be cheaper because we aren't already using it. You are looking at the decisions from 2010 to 2015 to evaluate the situation from 2021. For changing technology, that's a really bad assumption. If nearly all the market for CPUs is Intel, then AMD comes out with a far better deal than Intel, do you evaluate how much better AMD is by the installed base across all computer? Of course not. Check out what is being planned for the future. Some of the decisions are not great, because utilities don't yet know that storage is super cheap. But you'll find that in price responsive markets, nearly all new planned generation is wind, solar, and storage. Along with a few new gas plants proposed by people hedging against the dominant tech, or just through inertia.