Besides, Frodo and Sam didn't even fight Sauron. They just sneaked through Mordor and burned his ring in a volcano. And they barely managed to even do that because it required Aragorn and Gandalf to nearly sacrifice themselves and the armies of mankind just as a diversion. So to imply the forces of Sauron were weak in the books is absurd.
What really defeated Sauron was his inability to contemplate that anyone would ever wish to destroy so much power as the "One Ring".