One, the people who benefit from fossil fuel consumption are too diffuse to easily tamp down on.

Two, we cannot replace fossil fuels in certain applications.

Three, even all the green technology will need lubrication from something, unless we plan on moving back to whale oil (not exactly a renewable resource), we're stuck with oil based lubrication. Silicone use can be expanded, but it's not a 1:1 replacement for most oil based products. Burnable fuel is still a byproduct of this production.

Four, we cannot replace non lubricant petrochemical production at all, oil will still need to come out of the ground, and we will have fuel as a byproduct of that as well.

Fuel will continue to be available at a minimum as a byproduct of lubricant and petrochemical production, so while I think we can eliminate at least 50% of fossil fuel consumption - I just see no way to get to 100%. Getting to that 50% requires a whole lot more nuclear power than we have been willing to build.