If we care about eliminating fossil fuel usage, we need the gradient in the renewable uptake to high enough to cause a catastrophic shock to the fossil fuel technology and delivery chain. If it is too low, it renewables will drive down the price of oil, causing a jevons paradox follow on effect, where the price of oil falls, but because the infra structure is already in place, it is easy to use (infra can be useable but decay over time). Worst possible outcome is that the oil supply redirects to the developing world and millions of lawn mower style engines are put into high utilization.
Fossil fuels need a total shock to the system to end their use, otherwise we will indeed burn everything that is in the ground.