They were still pretty hard fighters for prissy nobles. The problem is that they refused to accept and understand the role of infantry, ranged attacks and light cavalry in warfare. The Knightly charge could be devestating when used properly, like say when infantry engaged the enemy from the front, set them in place, and then the Knightly charge rolled in on the flank. Frontal charges could even be pulled off when archers and artillery broke up the formations and infantry could be pulled up in time to prevent reserves from flanking the Knights and destroying them. Sadly, most medieval European commanders didn't quite understand that. They were convinced that the Knightly charge, and the charge alone was enough to defeat most opponents. Even when the overall commanders tried to used combined arms, sometimes the Knights just didn't listen. At Crecy, the French Knights rode over their own infantry and mercenary crossbowmen because they were tired of waiting for them to disrupt the English lines. At Nicopolis the King of Hungary begged to be allowed to send his 30,000 infantry and dismounted Knights against the Turks in the first wave, but John the Fearless opened the battle with a reckless Knightly charge anyway because he refused to let the lowborn infantry take from the Knights the glory of the vanguard. Richard the Lionheart at Arsuf had to personally threaten his Knights with extreme punishment to keep them from charging out of his defensive box. Even with that, they still charged earlier than he would've liked, but fortunately it was late enough in the battle and the effect of the English crossbowmen had been enough that the charge worked. The Knights could end up being a good commanders worst enemy. This is why great generals like Edward III, Edward the Black Prince, Henry V and others were very wise in employing their Knights on foot, where they couldn't mess up the whole works and ride off recklessly into battle.