MacDonald gets away with his stuff because he makes better decisions (still not always great, but compared to Graves he's the smartest man alive) and he's actually a pretty damn good skater. Along with that, MacDonald also has really high end hockey creativity. Many of his plays are against the grain in a good way. Sometimes they bite with a terrible turnover, but if there is more good than bad... you accept it. I'm not comparing here, but it is kinda like Zegras. He's going to make some really bad plays just because he's trying something... but if he pulls off 20%, he's creating some great scoring chances. MacDonald has a little of that in his game. Which has honestly, probably killed many of his chances at ending up in the NHL. NHL coaches want their lower guys to be safe all the time and coach out the aggressiveness. If you do that with MacDonald, you have a meh 7/8 guy.
With Graves, you get what he is now... a bottom pairing guy who is a bit frustrating. If they let him off his leash, he'd probably be a better defensemen... but he wouldn't be a defensemen you want on a contending team. His cons would just be too much. Would be a fantastic guy for a team rebuilding or just trying to get into the playoffs though.