The fault in your logic is your failure to account for the extrordinary difference in timescales involved in the creation of tablets and ferns.

It's worth remembering that Charles Darwin was a geologist by training. At the time, geology was a relativly new discipline, and the first line of scientific inquiry that demanded any concept of deep time. Its development signaled the dawning realization that the Earth was a lot older than anyone had previously guessed ("possibly a billion years" speculated Charles).

Acquiring an accurate measure of the timescales on which geological events played out is what set the stage for an evolutionary theory of life's development. Indeed, the theory of evolution is virtually inconceivable in the absence of these scales.