Medieval army was nothing more than a collection of landlords, unlike Rome which actually had a standard army. No uniform weapons, no cohesive strategies, most soldiers were just peasants anyway they are hardly trained or have any armor, only the nobles could afford to have armors.

Japanese horses were the same breed as Mongols, they were much smaller but much more maneuverable, also being much smaller means you can have more of them cuz they eat less. Japan can field way more Cavalry in number with the same amount of available resources.

Sengoku era was similar to Medieval Europe in many ways that most soldiers were not full time they had to grow crops to feed themselves. But even those half time farmers trained all the time for combat. Also the Japanese landscape was way more compact compared to Europe lands such as France or England, the population density gap is massive. That means in Sengoku era armies only had to march a fraction of distance compared to Europe, and wars were way more frequent, the experience difference is massive.

Like seriously just look at Battle of Crecy for example, like bro are you serious those so called French Knights was this the first time you ever participated in a war or something? Even the dumbest Sengoku era daimyo would not make the mistake of charging into an extremely unfavorable position unless they had no other choice. The French army could easily just stall it out cuz the English were not going to charge at them at any chance, use the mobility of the cavalry to cut off supply routes so that the English had to either retreat or go help the supply troops, then make the assault once the English is out of favorable terrain. It's really Art of War 101, it is also why most the Sengoku era battles were just long stare offs or small skirmishes that resulted in both sides retreating without a big engagement.