Think about it - all the most easily extracted fossil fuels, the stuff near the surface, are already exhausted. And, to transition to sustainable energy, you have to bootstrap manufacturing with fossil fuels, since mainstream sustainable energy requires photovoltaic cells and controllers and electronics.
I think that might be pessimistic.
We have fossil-fuel free substitutes for a lot of chemical needs. It’s just that right now, many of them are more expensive or smaller scale than just riding the petroleum dragon.
If the easy option isn’t there, we can still move forward, but it might be slower or require different tradeoffs. For example, plastic might be precious and used judiciously. It might be 500 years from “first hydroelectric dam” to “ubiquitous rooftop solar” instead of 150.