Nothing in this world remain static. In these four hundred years, the people of the grassland also learn the tactic of the settled people.
And they modify it to suit the people of the Steppe.
Roma on the other hand once had been raided by the barbarian tribes.
And the barbarian tribes at that time from the cold lands reached Roma and at those times, every statesman in Roma itself feel that Roma was about to fall.
Hence, they never relaxed their vigilance against the barbarian tribes that surrounds them.
Of course, if they could have integrated the barbarian tribes around them successfully, they could have it easier.
After all, those barbarians' tribes also yearn to become Romans
But just like any other empires and just like any other civilization of this era, there is this great distinction between others and you.
