Kupchak cannot be blamed for all of the Lakers woes. Especially in the area of trades/free agent acquisitions, or the lack thereof. Remember, this guy has put together some interesting moves to improve the club, but they've been shot down by Buss on account of $$$.
West, the genius that he is, did a lot of his magic before the latest NBA salary cap infrastructure was implemented after the lockout season. You notice he hasn't pulled any rabbits out of his hat lately. It's very difficult to get lots of good players nowadays. You can get one or two great players, but after that, adding those extra pieces is the hard part. It doesn't matter if you have Bill Gates' pocketbook (although it helps), the trade/free agent business is very tricky.
So let's see what Mitch comes up with this summer before we pass judgement. I'm going under the assumption that Buss has given him the quasi-green light to do whatever necessary to improve the team.