It's not clear to me how current market prices contain enough information to support or refute the assertion that renewables won't be able to supply enough for

It's not clear to me how current market prices contain enough information to support or refute the assertion that renewables won't be able to supply enough for a hypothetical future where fossil fuels are no longer used even for transportation. I think you need to also demonstrate that renewable energy prices can remain low even when required to scale up significantly beyond current levels, and that we won't run out of locations amenable to cheap and easy deployment of wind, solar and hydro power.