The presidential pardon is one of the biggest flaws in the US political system, in my view. Why would any system be written to assume the judgement of one person, even an elected person, was more reliable than the multiple layers of judiciary, with its reviews, appeals and other checks and balances?

it's not a great one, but philosophically it's a final check against the failings of systems by asking one person if conscience still allows a decision that systematically made. i think it hasn't been used nearly widely enough as times change and that let the political abuse of it dominate.