In essence, they are basing the Future Energy Scenarios around an energy scarce world with low EROEI and in many cases intermittent and sometimes unproven technologies. The mitigation for intermittency is both expensive and unproven. What could possibly go wrong?
My own belief is that we should be basing our future grid largely around abundant nuclear power, and work to address the apparent cost and time disadvantages.
https://davidturver.substack.com/p/national-grid-fantasy-energy-scenarios