This feels like that Futurama episode where Farnsworth discovers the last particle and descends into panic, realising he has nothing else to do. However, in my opinion, asking why there's nothing else is also a valid question to consider, even if we suspect there's something more to what we've seen so far.
Also, perhaps it'd be a tad bit more accurate to rephrase it `particle physicists`, not `physicists` -- even though it's totally exaggerated anyways.
Science has had countless cycles of believing we had discovered, more or less, all that was to be discovered and the remainder would come in sorting out things to another decimal place. Then a revolution, sometimes in short order, sometimes centuries later, comes around and emphasizes our ignorance and arrogance.
So at any given point you have two options: that we've finally reached "the end" - this is it and we can go no further. Or that we're at yet the latest cliff-face searching for that ever-elusive path through. I would always bet, hard, on the latter. At least if I could live forever, because even if I am right there's every possibility, if not probability, that none of us living today will be around to see it shown.
The notion of being able to discern all the fundamental laws of the universe while living on a single isolated grain of sand in a beach of ever more bizarre discoveries stretching out endlessly in all directions just seems improbable to me, at best.
Also, perhaps it'd be a tad bit more accurate to rephrase it `particle physicists`, not `physicists` -- even though it's totally exaggerated anyways.