Instead of accepting that natural limit of chemical combustion, scientists theorized that an electric propulsion system could put far more energy into the propellant via electricity. The pioneers in rocketry were aware of CP's limitations. In one form of electric propulsion, electrothermal, we use an arc that has about the energy density of a lightning bolt in heat. So the speed limit jumps to about 45,000 miles per hour. Ion propulsion introduces even more energy and can go to 100,000 mph now, with faster speeds on the horizon.
Chemical propulsion produces higher thrust.
It takes EP much longer to get to high speed. EP is used once a craft is in space. It can't provide the thrust to accelerate off the ground and into space. Gallimore uses the analogy of the tortoise and the hare to compare the systems. Chemical propulsion burns all of its fuel in several hours at most, then coasts at that speed in space.