Pardon power as a liberty preserving safety valve
Back in 2006, an exotic dancer and convicted murderer fabricated an allegation of "rape" against the lacrosse team at Duke "university." The rape never happened, but had the accused been poor and black, they most likely would have went to prison. Because they were wealthy, they had the resources to fight a corrupt system and exposed the criminal behavior of the prosecutor.
On his podcast, Ben Shapiro has been criticizing the power of the President to pardon people. Among other things, Shapiro said "Either you believe the criminal justice system works or you believe it doesn't." That is a false choice. It is possible to have a good system that occasionally fails, especially in a nation of 300 million flawed human beings. Sometimes people make innocent mistakes. Sometimes people are overzealous. And, yes, sometimes law enforcement will outright frame an innocent person for a crime that never even happened.
(Obviously, the President does not have the authority to pardon state level crimes. governors do, so the arguments here apply to them.)
Pardon power is a safety valve against these abuses and errors. Sometimes, mercy is warranted and sometimes the punishment is excessive compared to the crime. Over the last few generations, pardon power has become even more important. As government grows bigger and legislatures pass more laws, the pardon power becomes more important. In fact, it is estimated that most people have committed a felony at some point without realizing it - and that can include unintentionally making a false statement to a federal official.
Yes, pardon power has its roots in the tradition of monarchy. That does not mean we should abandon a power that can serve as a check on an overzealous state persecuting innocents or punishing lawbreakers far out of proportion to their crimes. Given how often prosecutorial power is weaponized for political grudges, it is critical that this authority be maintained.