Not swapping to a role not filled isnt throwing

Not at all.

You are claiming another player ruins your fun by playing the ‘wrong’ character

I am saying that the player in question has a right to their fun same as you do. Your rights to have fun dont extend to controlling what any other player does for their own fun

Similarly, if you are in the school cafeteria with me and you are only happy if you get to eat not only your own lunch but mine as well, you have extended yourself beyond your rights

You’re not getting that the hard counter is 1) your opinion and 2) irrelevant. If I want to play character x, and you want me to play any character other than x, I am fully within my rights to play character x.

and yet, there is no requirement that any player do so

optimal - yes

required- no