And will probably become more accurate still, correct?
Radiometric dating (discovered in the first half of the last century) enabled the first measurements of the age of rocks with any viable degree of accuracy. Using different isoptic rates, statistical uncertainties of <0.1% in the age of rocks 100's of millions years old has been achieved in some circumstances.
Prior to the discovery of radioactivity, estimates of the age of the earth had little accuracy, and the practitioners of geology at the time knew that.
Science continually refines its results - it rarely (if ever) needs to dump them all and start from scratch.