Despite your claim, during the early modern period (1400s to the 1500s usually), other types of infantry were employed, and to much success: pole-armed infantry was really widespread, such as in England even into the XVI century like at the battle of Flodden - where the english bills defeated the Scottish pikes. Also in the italian peninsula, mercenary soldiers used to fight in heavy armour, on foot, with pole-axes and similar weapons (but this "condottiere" manner of fighting was becoming increasingly antiquated) and managed to defeat the swiss phalanx on some occasions.

Even during the height of the pike phalanx in modern europe, such as during the "reign" of the spanish tercios on the european battlefield (late XVI century until at least the battle of Rocroi in 1642), the phalanx was used in combination with many other type of infrantry: mainly sword and shield soldiers and arquebusiers - another exaple are the longsword armed zweihander in landsknechten-like armies.

In fact a combined arms approach is fundamental with the pike, since a pike armed soldier is generally ill equipped to face theraths from directons other than the front.

Considering this, the decline of the macedonian phalanx can bee seen more from a tactical point of view: under the leadrship of the successors (mainly Antigonid macedoninas, Seleucids and Ptolemaic egypt) the reliance on the phalangite was somewhat increased (since they were mainly used to fight among themselves) and less importance, to an extent, was given to the supporting troops (particularly to those dedicated to flank and circle the enemy lines). So they faced serious defeats from Gallic opponens, fighting more in a "small units tactics" manner, and later the Romans. In fact the roman leadership was well aware that a pike wall was normally unpenetrable, so they relied more on fighting them on uneven terrain ( to disrupt the phalanx) like at pydna or by winning the flanking maneuvers.

Conversely the modern pikemen was slowly phased out of service (or at least the active service) during the course of the XVII century because of the increasing effectiveness of musket armed infantry (exspecially after the introducton of the bayonet).

In either case, spear armed infantry was always present on the battlefield, both before and after the decline of the macedonian phalanx, so its end was not the end of spear fighting that remained the main weapons used in war until the modern age - many fighting manuals, like the Flos Duellatorum by Fiore de Liberi (1409), of the XV and XVI century feature spear tecniques along side long and arming sword ones.

The aformentioned Scotland represent an example of the usage of long spears in battle during the middle ages, in occasions as the famous battle of stirling bridge the spear spiked schiltron defeated the english cavalry; spears of various lenght were the weapons of choice of many medieval armies.

Sticking to your question, the equipment also was generally different (in its role): the macedonian phalangite was basically an hoplite with a longer spear and a smaller shield, laced to the shoulder so that he could wield the pike woth both hands. He usually wore a body armour (being a linthorax or some sort of mail protection), and was regarded as being heavy infantry - opposed to lighter equipped peltasts as an exaple, while the modern pikemen was not really heavily equipped for his age, in comparision with dismounted man-at arms who used to wear a full plate of armour (at least until the early xvi century), usually being armed with just the pike and a sword, not always wearing a body armour (such as a cuirass).