I’m sorry, but believe that says far more about those players than the developer, “This particular combination of skills, that I’m in no way required to get nor obligated to use in any specific combination, makes me too strong, and being able to have that voluntary option and/or other isolated players being able to make that choice separate from my own experience upsets me to the point I need to not play the game.”
I’m honestly not even trying to be that sarcastic or funny - that’s literally the conclusion I’ve drawn from this.
To answer your more specific questions
Because I can’t simply choose to make enemies have higher life and/or more tactical AI. Player has no say in that.
And I can’t simply choose to make the game not crash, or make save files corrupt or make things freeze. Player has no say in that.
I can however simply choose to not utilize optional skills that I believe are detrimental to my experience. Player does have say in that.
In this case, considering it’s our (players’) choice how to develop our characters/soldiers, I don’t see this as an actual issue.
To use a hypothetical example: Three skills each give a 100% damage bonus. Individually, those are feasible skills. They provide a boost that makes them worth the investment.
Now, if I, as the player in complete control of what skills I get, don’t want a 300% damage bonus, I make the choice to not click those very specific buttons together in a very deliberate pattern that I know would give me a 300% bonus and develop my character/soldier in a different direction. I may take the 100% bonus or the 200% bonus, but I will not take the known, optional action to activate all three of those skills. What I, myself, don’t do, is petition the developers to remove that option from those who do want a 300% damage bonus.
Don’t really want to just blanket nerf any/all of those combinations because it does take away from their individual viability - and we don’t want to individually destroy the skills.
The other option is simply coding in “can’t use these together”. Problem is, that doesn’t provide you any experience that you don’t already have (by simply chooseing not to use them together), but it’s at the cost of keeping those who want the stacked bonus from having the option to have it. It didn’t really “boost” your experience and it likely negatively impacted others’ experiences. If the change to the game is a net-loss for player experience, that’s rarely ever a wise change to make.