The OP has somewhat of a point--the best way to build an NBA dynasty is to land a top 5 NBA player and add to that. As has been noted many times, the majority of NBA championships can be attributed to a dozen or so NBA players. And while opinions vary on Love, I think we can all agree that Love is not a top 5 NBA player on the same level as LeBron/Durant, etc.
However, what the OP is overlooking is how incredibly hard it is to land one of these players. He seems to think that simply by tanking and building picks that such a player is going to fall into our lap. But we've seen firsthand how that doesn't often work out with not only what happened this year, but also what happened in 1997 and 2007. Moreover, think of all the teams that have cleared enormous amounts of cap space to try to land the LeBrons and Duncans of the world when they've been free agents, only to be spurned by these stars.
Unfortunately, unrealized potential allows one's imagination to run wild and draft picks are the ultimate manifestation of unrealized potential. We can fantasize about how the next LeBron (or even the next Rondo) is going to fall into our laps. However, we too often forget that more top picks in the draft turn out to be Kwame Browns rather than LeBron Jameses and that most teens to twenties picks turn out to be Kedrick Browns rather than Rajon Rondos.
Danny proved in 2007 that by assembling a triumvirate of very good (but likely not top 5 talents), that you can win a title. Had a few things broken our way (for instance, KG, Perk, Shaq, and Rondo all not facing their injuries) we could have potentially won multiple titles. So while it'd certainly be better to get LeBron than to get Kevin Love, I don't think we can dismiss his acquisition because he's not a top 5 player.
Rather, I'd look at it like this: pairing Rondo and Love together puts us one star away from being a contender. Will it still take some good fortune to find that other star? Absolutely, but every NBA champion has had a little (or a lot) of luck (just ask the Spurs, who had Tim Duncan fall in their laps because of an injury to David Robinson). But maybe a trade presents itself next year or the year after. Maybe Danny can find another Rondo-like talent later in the draft. Maybe Jeff Green finally gets his head on straight and becomes the third star we need.
All of these scenarios are much more likely than us entirely blowing it up and then hoping through the draft and free agency that we can somehow come up with three stars or more through that process.