Even if there is something to "come after us", and it's intelligent, I've seen it argued that most if not all of the easy to get "advanced" resources (eg oil, some minerals) have been harvested. For a new civilization to rise and reach our levels again from scratch would be very difficult.

I haven't checked the veracity of that statement recently though, I'll see if I can't find it again.

Without any reference: that makes a lot of sense. We are essentially withdrawing stored sunshine from 100's of millions of years ago to re-use it today.

Obviously true for coal. Far less obviously true for simple hydrocarbons, which appear prevalent everywhere in the solar system.

Most minerals can be re-extracted from our ruins; energy resources are irreplaceable, but mining former cities for steel and copper is likely to be easier than purifying them from ground deposits.

Hm... maybe. Especially copper is not so easily separated from the substrates in which it is used, for an electric motor it is fairly easy but all of the copper embedded in millions of miles of wiring (which of course you can cook, but the fumes that will produce are going to be extremely dangerous, think dioxins) it may not be quite so easy.

The advantage of most copper deposits in their natural form is that the rock can be crushed and the tailings are uniform and mostly heavy and inert. For what you'd get out of a 'former city' it would be far less dense in terms of copper and steel than a mineral rich vein. I think before we'd go for the cities themselves there would be the dumps and then the deposits that are today not economically feasible. Long after that the cities.

That's fine. Intelligence is an evolutionary dead end. It leads to unsustainable behavior. Maybe there are space-faring creatures, but I think they are more likely to be bacteria or maybe a tardigrade-like being that are hitching rides on comets or planetary ejecta.