Ummm what? I don't think you understand how damage works. If you had a riven mirror math and one had conquered doing only true damage and giving nothing else and the other had electrocute the one with electrocute would win and its like this for basically every match up your not fighting a tank.
Like conqueror is taken more now after the rework and the pervious version give DOUBLE THE TRUE DAMAGE.
Like I'll do the math for you.
If a champion has 50% damage reduction with is a reasonable amount late game for any champion. You deal 1000 damage you only deal 500, now if you have conqueror it goes up to 600 meaning it give you 100 more damage. Like that's is not a lot and you have to keep in mind that basically every conqueror user deals damage over time meaning the true damage means even less on a non tank which is the majority of champions.
Like 10% true damage sucks in comparison with almost every rune since they give more damage again the only time it matters is vs a tank and it will still do basically nothing early game even vs a tank.