Look at fossils as example. Yes, we have quite a lot of them but they stretch over a couple hundred million years, so imagen the things we don’t know about these periods

I get your point. But then again look at how many fossiles there still are. And those are all biologically, easily degraded. We’ve build quite sturdy things and even if only a tiny fraction survives there should be plenty for future archeologist to figure out that there was some civilisation at work.

With the extend that humans have changed the planet, we should leave a very obvious geological marker. Like suddenly there is plastic in the sediment layers …