The important to thing to remember is that the phalangite was only one facet of Alexander's army. The Macedonian combined-arms approach employed doses of cavalry, phalangites, skirmishers, and good old fashion spear/sword infantry to great effect. The phalanx itself didn't win Alexander the world. It was a symbiosis of different elements that allowed Alexander such success against the enemies he faced.

It's also important to realize that the army of Alexander's time was vastly different from the armies deployed by the Diadochi, the Successor Kingdoms. Gone were the regular infantry to hold the phalanx's flanks and the skirmishing arm was greatly reduced as well. Even the famed cavalry Alexander used to hammer his foes into submission had been decreased in size. The Diadochi focused instead on just increasing the number of phalangites and using more esoteric weapons such as war elephants. Compare the force Alexander used in his conquest of Persia with the army Perseus employed against the Romans and you see just how different the phalanx had become. Alexander had thousands of phalangites, but with them were thousands of regular infantry, skirmishers, and both light and heavy cavalry. Perseus had phalangites, a small amount of cavalry, and that was it. Is it no wonder then, that the Romans were able to outmaneuver the phalanx at every turn? Nevertheless, the outdated phalanx was still able to give a good account of itself against the Romans. Both at Pydna and Cynoscephalae, the Romans were hurled savagely back whenever they tried to close with the Macedonians head on. It was only when the Macedonians gave chase to the withdrawing maniples that the Romans were able to exploit the gaps left in the phalanx and win the day.

Transport the army of Alexander onto those same battlefields, with its varied approach to warfare and focus on combined-arms, and maybe historians today would be extolling the virtues of the phalanx instead of kowtowing to the legion.

Although it doesn't cover the demise of pike warfare in the classical period there's some wonderful insight given to the rebirth of pike formations in European warfare in the Early Modern period and their development from "pure pike" to "pike and shot" formations here .