a lot. observing and understanding gravityWhat are we missing?Absolutely not.
requires much more than dropping a stone.
What is? A dropped stone? Oh no , far from it. First you should record the time of the fall. You should use stones of different weights. You should somehow estimate the effect of air resistance. Etc. Aplying maths and logics may, or may not, enable the researcher to find some equations that models the motion of the stone. It will be a big leap from that to actually realize that it is the mass of the earth that pulls on the mass of the stone...It is the full expression of gravity.
And yet bigger to realize the general theory of relativity.