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We can't even measure the gravitational constant to more than about 4.5 significant digits. Most other natural constants are in the 7-12 digit range and improving along with our technology. Measurement of big G hasn't convincingly progressed since the vacuum tube era.

We have a lot more to learn about gravity, especially at laboratory scale and smaller.

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As a laboratory-scale experimentalist, I heartily agree, but must also point out the existence of compelling precision equivalence principle tests.

While we can only measure G to ~10 ppm, the equivalence principle has been tested at the 10^{-14} level (and ~10^{-9} at meter-scales). The EP is the property that makes gravity really special and simultaneously the thing that makes gravity hard to test.

The core assertion that all things fall the same way is axiomatic to GR and has been very well tested. We have everything left to learn about gravity, but at the same time, GR has held up far better than it "should" have against a battery of really great experiments.

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