The problem with OKC is clearly Carmelo Anthony.
Yes, we can talk all about Westbrook's stat padding and being inefficient, and PG13 has had some cold moments in the series as well, but Carmelo just looks bad.
He's always been a liability on the defensive end, and so when his shot isn't falling (like now), he's just a black hole on that team. Seems to be he just hasn't brought into the system with PG13 and Westbrook now on the team and hogging the shots as well. (Doesn't like being the 3rd option)
But part of it you can say is on Westbrook. He needs to get his team more engaged and defer to the other guys at time instead of trying it all alone (which he tends to do when the going gets tough).
And I see people say Scott Brooks needs to draw up more open plays/looks for guys, and I would have agreed after Game 2, but after seeing the last few games, I don't think you can entirely blame him. I was watching parts of Games 3 and 4, and OKC were just bricking too many open looks (especially Carmelo). Not sure what Brooks can do, and credit to Utah, they're protecting the paint relatively well. Adams can get his, and Westbrook + George can occasionally drive and draw the foul or score, BUT Melo is simply the iso-jump shooter who can't shoot right now.