I sometimes get the sense that the Greeks, with Alexander’s long spears, formations, and short hair cuts; and the Romans, with their formations, etc., had better organized and trained armies than in the medieval ages where its was largely unarmored peasants with farmer tools supporting heaavily armored and armed aristocratic knights. Is that correct, if so why were the medieval ages so backwards? Feudalism? Or am I just totally wrong (as is the answer in most instances)

As @warsofasoiaf​ will tell you, this is not correct. Yes, it’s true there were poorly- armed, armored, and trained peasant levies on occasion, but the majority of infantry were professional soldiers, be they archers, dismounted men-at-arms, pike/spearmen, etc.

It’s true that knights were the major focus of medieval armies, but it’s also true that the battles of Crecy, Poiters, and Agincourt which showed their fatal weakness in the face of archers protected by disciplined infantry also took place during the same period.