This is pretty much exactly what happened with the tomb of the Qin First Emperor, a site of obvious historical importance in a country with extreme respect for history.

And I'm given to understand that it is now standard practice elsewhere to try to leave most of a site buried, so that future archaeologists with better technology may be able to dig in the more pristine part.

So archaeology has certainly developed in this direction, probably through the experience of wanting to test new techniques on old sites and not being able to. I'm not sure why this concept would apply to "scientists" in general, though. If you're looking for facts about the present, you can't really contaminate them by investigation.