Which also seems to imply that the human race is getting smarter(comparing people with the two greatest physicists before the 21st century)!
No, but physics is getting more and more complicated and today it would be impossible to be active in as many different areas as e.g. Newton was. It has nothing to do with intelligence, there just wouldn't be enough time.
A 100 years ago the total number of full time physicists in the world was probably about a hundred or so (at most); i.e roughly the number of people that belong the physics department at a major university today.
Another example: at the turn of the century Kammerling Onnes had the biggest and best research lab in Europe (probably the world), most of the time he had 4-5 people working for him (most of which became famous).
Compare that to modern projects like e.g. the LHC.
The point is that there are plenty of very intelligent and dedicated researchers around; it is just that in order to get somewhere today you have to focus on an extremely narrow field and you need a LOT of resources. Hence, no single physicist working today could even have the kind of impact on science Newton and Einstein had in their days.