I think there are consistencies in your second paragraph. You don't buy the low-hanging fruit argument, however you then state that we need to spend decades on

I think there are consistencies in your second paragraph. You don't buy the low-hanging fruit argument, however you then state that we need to spend decades on in-depth studies. Well, those are exactly the opposite of low-hanging fruit, those are extremely hard-to-reach and abstract fruits that the vast majority of the scientists of the past would have been unable to grasp, simply because they did not have access to all the foundations we do today. You can't attack Poincare's conjecture without basic arithmetic, nor can you understand antibiotics without a knowledge of infection and germ theory. Look at some of the most sea-changing discoveries in the history of science and you will see it was not the result of decades of laborious and thoughtful calculation and musing. Penicillin was discovered by coincidence or luck; the production of rubber for tires was also lucky. How about chance astronomical observations like an eclipse, whereby a great deal can be learned in a fleeting moment? How about displacement of water, or the pythagorean theorem, or Michael Faraday's cheap and quick experiments into electricity. These are not tours de force, by and large they are little fun divertissements, interesting observations with great consequences. I think there's no doubt that MANY of the low hanging fruits have already been plucked. It's the same way in many other fields, such as music, art, computer science, or anything else. People naturally discover the simplest things first, and then build upon those, with later discoveries taking far more investment of time/learning to even be capable of understanding, let alone discovering.