the second issue to overcome is variability - i.e., to keep the lights on you need to be able to turn generation up in real time to meet demand. Because that's not how solar and wind farms work, they pair with storage. Put them together for the needed flexibility.

Fortunately, around 2020, storage-integrated variable facilities became cost competitive with combined cycle natural gas. NREL - for the desert southwest and plains, at least.

So really all of the biggest economic barriers have been removed. Every major utility in the southwest is already pivoting, but not as fast as some people would like. A few lesser problems are on the horizon - first-order voltage modulation without synchronous machines is hard, and the vast majority of solar&wind equipment we've installed so far isn't designed to do it. the 2016 blue cut fire

I always get a very mixed response for talking about this stuff - I worked for the first US developer of utility scale solar. At the time; there were problems getting banks to lend on these projects. I frequently spoke with the leadership of Edison, PG&E, SDG&E, Pacificorp.... about these technical challenges, and how to meet them. Unfortunately CAISO chose to overbuild without requiring flexibility (SCADA curtailment); they lean on exports instead, which isn't scalable - the EIM will become less of a solution as more participants overbuild variable resources.