Comment 8 by Atheist Mike :

Western economies are going to hell and there's no major conflicts to force us into spending more into futuristic innovations (unlike in the 20th century where there was WW2 and the cold war). I'm sure corporations will continue making minor innovations throughout this century but I don't expect much from government-funded researches.

That may have something to do with it, but Einstein's relativity & the Quantum Revolution were not war-motivated or the result of major government projects. My argument is that we've picked all the low-hanging fruit and that what remains to be discovered it not linear but exponentially more difficult/complex/costly.

Think of travel to the nearest village, town, city, country and the Moon. Suddenly the next step (planets, stars) are orders of magnitude more difficult than going from horse to sail to steam to internal combustion engine. It may be like that for many areas of science.

I don't believe we've come to the end of science. But what remains is far too difficult for us, and that's why the intervals between revolutionary discoveries are getting longer, even if there was a war to aid funding.