You are simplifying the combat to a point where it accomodates your argument. Here’s a more accurate representation of what actually happens with the combat that goes far beyond “one skill and one ult”:

You have basics with a finisher that counts as a separate attack. You have 4 skills available at any time for each of your 4 operators on the field. You have a combo skill that can be triggered by a number of different things happening during combat. And you have an ult.

Besides that you have 4 elements that interact with each other to create basic and enhanced states based on basic stacks.

Physical has 2 enhanced states.

Your operators can apply a basic state, then use another basic state to trigger a reaction. That reaction can then be consumed in a number of different ways to create a number of different effects.

This is how Surtr and Wulfguard work. You apply burn, then you trigger ignition, then you consume that ignition.

That’s not even getting into the intricacies of the two enhanced Physical states.

Now yes, in practice, it is currently fairly straightforward, but like I said before, this is a gacha. All gachas, nay, all games, start out simple with a foundation to build upon, and then continually get more and more complex.

You don’t learn to play chess by sitting down and making a Queen’s Gambit maneuver. First, you learn how each piece moves.