Why am I bad in tactics?

[ReluctantSamurai]

Doesn't always work.

Probably true. However, practicing 1 vs 1 isn't simply about winning or losing the battle. With only two units involved, you can zoom in close and actually watch the action, without distraction, to see how a particular unit functions in battle.

As an example, for the longest time I never realized that elephants don't actually rack up a lot of kills, but instead cause major disruption in enemy formation leaving them vulnerable to a cavalry charge. In-game, with many multiple units engaged, it was difficult to see. But in 1 vs 1 it became clear as day. It took seemingly forever for the ellies to kill or rout the enemy, and if the action went on long enough, the ellies themselves might rout because of fatigue. That caused me to change my tactics with ellies. I began stacking a cavalry unit in echelon, had my ellies charge to a point beyond the unit they were attacking, and sent in the cavalry charge immediately. Devastating.

In RTW, Cataphracts have two weapons, the primary spear, and the mace. The spear is best used for the initial charge, and then when melee ensues, switch to the AP mace. It's much easier to practice, and actually see them switch weapons, in 1 vs 1 than with multiple units.

But yes, to get closer to what will actually occur in-game, multiple units is better, but with some 1 vs 1 experience, you already know how your units will behave, and don't have to micro-manage as much