There are 44 four-star officers in the US military. But I agree with your point - they are often far behind the lines. Unlike in the Russian military, however, the U.S. and its Western Allie’s trust their subordinate officers to run the battles. In Russia, the senior officers have to lead from the front. Given their valuable experience and training, such a practice is not bravery, but stupidity.
“The U.S. Code explicitly limits the total number of four-star officers that may be on active duty at any given time. The total number of active-duty general or flag officers is capped at 218 for the Army, 149 for the Navy, 170 for the Air Force, 62 for the Marine Corps, and 21 for the Space Force.”