The point wasn't that Giggs is a tip manager but that you can't complain about his lack of experience when you have in the past appointed a player with little managerial experience and what was Rodgers' experience? His failure at reading and Watford? He won't ever manage at United but he could be good enough for a side with lesser aspirations.
I get your point, in the past the club has used up and coming managers. The landscape has completely changed though, we are not in league 2 or 1, we're in the richest football league in the world.
Rodgers didn't have a playing career, he worked at Chelsea as a coach, was highly rated by Mourinho and had worked at 2 clubs as the man in charge. Also failure at Watford? Reading paid a million to get him! And finally, we weren't a Premiership side, we were in the championship (promotion looking unlikely at the time)
So if Rodgers is willing to drop down a league, why can't Giggs?
And how do you know Giggs will never be good enough for Manchester United, but he's good enough for Swansea now?