There's some value to "the President can correct some wrongs". There are genuine miscarriages of justice sometimes and it's kinda nice to have a release valve for them.

The recent presidential immunity decision just made the downsides way more likely.

It’s an alternative to coups and civil wars. The deal made in private conversations is something like “Give up power peacefully. Everybody gets pardoned and goes home to their families. Nobody needs to do anything crazy or violent out of desperation to avoid prison.”

Justice is a moving target mate. Should people who had a few pounds of reefer still be serving 30 year sentences? 90's adults would probably say yes. Today? Not so much. Part of being human is being open to the fact you were wrong. The Pardon is the release valve that lets the Chief Executive remove the targets the System has painted on people's backs in response to a clear shift in public conscience. The public in recent history, threw all prudence to the wind and put a con man in office. Surprise, surprise when a con man uses the office to do what con men do.