Well NPE is varied from player to player and everyone enjoys the game in different way and also react negatively to different thing. We are assuming in this discussion, the theoretical player is in good faith and not projecting blame or lack the ability to learn, rather the person want to enjoy the game and keep playing game.
Really though often many NPE moment can alleviate with communicating with your opponent in what kind of game you want to play. Casual, friendly competitve or hyper competitive.
like for a war game based on dice roll and also asymmetrical balance, there got to be a certain degree of acceptance that for army to be unique and still win the game of sigmar their going to have to be a degree of cutthroat mechanic. Ironjawz are melee only army, they got to hit you hard and fast and probably want to play for that double turn. Tzeentch is a magic army, they are going to be way stronger in casting and denying magic then the average army. KO/ Tau has a lot of Guns but have little to no melee, so they got to shoot their way to victory.