He's good. Some people over inflate his defensive gaffes. He has his moment where we used to call him the Muffin man, but he's very solid.
And he deserved every chance to grow into the NHL. Of course there are bumps on the road along the way.
Muzzin has a wicked, accurate shot when creeping in from the point. That wrister from the top of the circles has always been his strongest suit, but those chances have been fewer and farther between as the Kings descended into a team that could no longer create chances with cross ice puck movement. He will score a boatload of goals in Toronto from that spot.
He holds the blue line well, with occasionally huge hits, but his defensive game is just average. His stick isn't always in the best spot, and too often he will get beat from the boards to the front of the net on coverages. I don't really agree with Osprey about over-pinching or leaving the zone too early, that's not something I feel does more than any other blueliner with an offensive tilt to his game.
One thing to look for, the reason he gets beat from the boards, and why his first pass isn't always accurate is that he skates in a very upright fashion. He doesn't get a lot of leverage with his stick, and for a bigger guy he has a relatively small area of influence around him. He skates very well, but it's too easy to get in and around him.
Muzzin has a lot of sexy attributes, has a great attitude, and will improve anybody's top-4, he just isn't an all-world type of defender. His strengths do more than just cover for his weaknesses.