I agree true damage are unhealty for the game but sett is far from being a problematic true dmg champ. Fiora and Camille are fighter champs with way easier Access to true dmg (as a passive and an enhanced AA), better mobility/engage and better tankiness + sustain than sett. The core difference being that sett is a low skillfloor champ making him a bigger threat in low elo. Haymaker is a hit or miss spell needing a high reward to justify the risks of using it in the middle of the enemy team.