The longer the spear, the more important momentum becomes.
Spears were used in infantry combat, but they were primarily used in formation. They're not the kind of weapon you want to run off and 1v1 someone with. Which is why spearmen almost always carried a sword, mace, or axe when they had a spear.
A bit of a misconception.
The primary reason spears were usually used in formation, was because when not in formation spears were simply cumbersome to carry around -- ie. outside of war-time, where one would take part in such formations, the spear was a very cumbersome tool to carry around for a lot of obvious reasons. When someone would carry around a spear, when that someone wasn't a part of a mustered army, during peace-time, it draws attention -- in the same way a person carrying around a shield when not in wartime, that was not a part of the guard forces, would draw attention.
In formation or no, spears were the primary weapon.
Again: spears are an anti-cav weapon, that also happens to work far better on horseback than a sword, axe, mace, etc
It's alright if you want the spear to be the end-all, be-all weapon, but I don't believe TW devs share your desire to imbalance their game.
Spears were simply a universal weapon to fight against whatever the enemy.
A decisive example? Greeks -- entirely spearmen in formation. The classical Greeks did not use cavalry at all.
In other words, the spear actually WAS an end-all be-all weapon. In terms of efficiency, as well as actual combat prowess be it in formation or 1v1.
Spears already have a hugely important place in the grand scheme of combat. And they do their job well.
TLDR: spear are fine.
They are not fine.
The element that makes a spear a spear, is the range advantage it has over other weapons.
In the game, no other weapon loses its essence so easily. The very fact that most people give up thrusting spears and rely on swinging weapons if they want to use polearms as main, is because swinging weapons do not lose their essence as easily. The very fact that you need to build a character with very high athletics, to do well with thrusting spears, is also because that the spear loses the range advantage so easily, that they have to compensate and
"simulate" the range advantage by back-pedaling faster than the enemy can advance.
I am totally willing to wait until the perks "Push Back" and "Keep at Bay" start working to see if things are remedied, but even if those perks start working, it's preposterous in the way a main, fundamental advantage of the weapon is stripped away and thrown in as a perk.
Imagine a scenario, where your bow only fires up to 10m distance. And in order for you to shoot further, requires you to skill up over 100. That's the predicament the spears are in right now. (Actually, have been in since MB1)