They're in the classic veteran playoff team trap. Rookies don't really help them, draft picks don't really help them. Because generally speaking, they want guys who can plug and play and defend, and who aren't going to wilt under the pressure of the playoffs. Right, wrong, or indifferent -- rookies can't be counted upon for any of those things [I'm not suggesting that there aren't rookies out there who aren't capable of doing so]. They're also not drafting at a spot at the end of the first round where they are likely to get surefire contributors.
So, you hope to catch lightning in a bottle with older, proven vets -- some of whom are willing to play for less money. They absolutely caught lightning in a bottle LAST year with Richard Jefferson. Ditto that scrub from Rutgers / Duke, who had the one big game in the finals. Deron Williams wouldn't play on 90% of the teams in the league, but the Cavs were hoping that he'd have a bit of gas left in the tank.
Problem is, those guys are getting exposed because there isn't the same type of dropoff when the Warriors go to their second unit.
I think that the main move you can criticize is trading Wiggins -- that might have been shortsighted, but I absolutely get why the Cavs did it. And they might contend that winning it all last year made it worth it, even if Wiggins goes on to be a star in the league.