Actually, it is hard for me to get this formulated properly, but it's not that there aren't things we know, it's that a theory about what happened can't be verified for sure because there is simply no way to test what happened in the past.
So, what you're saying is that, our conclusions about what happened in the past might have to be...
tentative?
All that is speculation, theory, the stuff that can't be proved or falsified.
Well, it can't be proved, but it can certainly be falsified. If the fossils weren't arranged the way they are, that would certainly falsify the historical evolutionary model.