re: Why can't LSU recruit and develop a good QB?

Gonna try to answer the question without feeding the obvious troll parts-
Yes, QB recruiting has been rough on LSU. And for everyone that keeps bringing up Mett, we developed him, but did not recruit him.

Pretty easy answer: against premier defenses such as Florida and Alabama would field, a decent mobile guy is better than a good dropback guy. Your O-line is not going to be able to protect the pocket all game, not when every other position is an even matchup. The mobile QB can roll or scramble and ruin an otherwise perfectly defended play.
Go look at Jordan Jefferson's overall career against Alabama, who was at that point playing at extremely high levels. Moved the ball well in a tight game at Bama in 2009, got a win in 2010, his running the option was the only offense we had in the 2011 win. Was he a good QB? Not by the eye test. But he was able to keep the defense honest enough. Mett was a far better QB, and 2012 showed if he had time he could produce; but 2013 showed if the line broke down he was dead in the water. 2011 game at Bama showed the same with Lee, the same game Jefferson was able to run the team to a win.

Add to that, La doesn't produce dropback QBs anymore, they're usu the best athletes. Look at LSU right now, Harris is clearly a great athlete. More to the point, Diarse and Magee were also high school QBs. Those types of guys are the ones you have to pick and choose from, locally (where you have the best chance of signing a guy as developmental depth).