Combusting fossil fuels has a peak efficiency of ~60% (around 40% for ICE).
I’ve no doubt it will likely be required for decarbonization, but I somewhat doubt it will be useful for grid electricity. It’s more likely (IMO) that the CO2->fuel route will mostly likely be used for things like airplane travel where the energy density of batteries is unlikely to get high enough to work well. (A battery plane with ~1hour flight is possible but it requires uber high density batteries). It might also be useful for generating fuel for shipping.