In some historical periods that was true. In others, not so much. The Zulu at Isandlwana were seasonal warrior-farmers, but they sure charged the British lines with their goat's hide shields and short, thrusting spears, and massacred the British despite the latters' technological superiority. Alexander's army comprised regular professional soldiers and they sure marched in a phalanx (the phalanx didn't quite charge as it was too slow moving to do so) and Alexander himself of course charged at the head of his Hetairoi. The armies of medieval feudal lords were in their majority levies, as you say, but the Crusaders, in the same time period, were for the most part elite knights who fought with unending courage (and commited incredible atrocities) against enemies many times their numbers. And so it goes.
As to bribery, sure, many battles were fought with money or politics rather than swords. Yet again others were not. Think of WWI for example, or WWII. No chivalric ideals there, but the battles were bloody and the corpses piled on high.
Btw, thanks for reminding me to read about the Khwarazmians.