Except if our society was to collapse there would be brand new massive veins of resources extremely close to the surface and with incredibly high purity in the form of the old cities and infrastructure that we already built. Eventually they would have to make some jump from recovering previously collected resources to exploiting new sources, but by that point they would already have reached levels comparable to us.
Most of the early industrial revolution was done with water wheels, steam engines came much later. Since most of the iron and copper extraction would be much much easier since you could loot them from pre-collapse cities, it could be a wash.
And of course if even a single library survives mostly intact then our successors will get an absolutely massive jump start. Just a single "principles of physics" college textbook contains centuries of research.
The fact we happened to utilize cheap fossil fuels does not prove that fossil fuels are necessary for an advanced civilization to develop. One might even argue our prolonged use of fossil fuels was a mistake.
Maybe we should have been extremely careful with how those energy resources were used instead of just using them for whatever or as if they'd never run out or have any externalities. Doing this in a way that's in the best interest of humanity, without repeating the mistakes of communism will be an interesting challenge for humanity in the decades ahead. That is assuming we don't develop some deus ex machina like cheap fusion power.
