Throw out the radiometric dating and what do we really know?
1) Light takes a long time to get from quasars to us, but we see them.
2) Early geological estimates for the age of the geologic column based entirely upon rates of sedimentation were still far, far over 6,000 years. Well over 100,000, IIRC.
3) Lines of evidence from molecular biology tend to produce age estimates for things like the emergence of reptiles from amphibians, etc., in line with (but usually even older than) evidence from paleontology.
The Earth is obviously old, period.