It is possible, but not certain, that a top 5 talent is needed to win a championship. It is not guaranteed that even multiple top 5 picks will get you even into the playoffs.
Cavaliers have had drafted 5 lottery picks, 4 in the top 5, two number 1s, one superstar and they still YEARS away from contending. That is after hitting the jackpot with Irving.
Kyrie Irving
Dion Waiters
Anthony Bennett
Tyler Zeller
Tristan Thompson
Why in the world would anyone want to run head first into that?
Bennett hasn't even played yet and Zeller/Waiters are going into a second year. Irving is a stud, I'd take that team over what we are looking at these days. Don't buy your argument at all.
When do you think the Cavs would be a contender? This season? Next season? 3 seasons have passed since they got Kyrie Irving and they haven't made the playoffs. Like you yourself pointed out Lebron didn't make the playoffs for 3 years and he's on track to becoming the greatest player of his generation.
People who want to tank think that once we land Wiggins it would be easy to build a contender. Yet Irving, Wall, Griffin, Rose, Oden, Bargnani, Bogut haven't reached the finals, and Howard has only reached the finals once which he lost. Lebron only won a championship when he left Cleveland to join a playoff team with a star in his prime.
The chances of building a contender around Rondo are way higher than tanking for a top 5 pick and building a contender around that player. Howard joined Harden to make Houston a contender. Lebron and Bosh joined Wade to make Miami champions. Gasol and Shaq joined Kobe to help make LA champions. Chris Paul joined Griffin to help make Clippers a contender.
The ONE example of quickly building a contender through the draft is OKC. To do that, you only have to draft Durant, Westbrook, Harden, Green and Ibaka. If Wiggins became Durant that would be a miracle. And then to hope for our next 4 picks to be Westbrook, Harden, Green and Ibaka is near impossible. That is IF we even win the lottery to get the number one pick. Even OKC didn't get the number one pick, they had to have the additional miracle of Portland taking Greg Oden with the number one pick so they wouldn't have!