How to fix a sloppy track without making it sound over produced?

Hey so I have a lot of old old tracks on my laptop from when I played in garage bands and recorded ... in GarageBand and some sound frankly sloppy so I wanted to patch them up and rerelease them for some friends.

However when I started doing it, the finished product loses its charm and sounds overproduced. It doesn't help that I don't have the original vocalist and I was only doing back up.

They're mostly two guitar, piano, bass, drum set up with some synth fracked sounds thrown in. If anybody has advice I'd be forever thankful!