It really isn't that complex. It's just so unorthodox that when trying to put the battle system in words, it comes across as overwhelming. Basically a lot of the same fundamentals carry on across virtually all battles and the differences between each battle involve strategizing around enemy/enemies positioning and how their armor gauges if any can be broken, and terrain differences.
Spending a bunch of time in the Arena early in the game helps to hammer in the game's systems.
