DDG won 4 Matt Busby player of the year award. He was the first goalkeeper to win it, the first player to win it three times in a row and the first player to win it 4 times. I think he's slightly better then tackles. SAF won a league title with DDG in goal and he had bailed out LVG and Mou in numerous occasions. Ole tried to replace him but he won his place back putting the most hyped bench player in United's history since Fabio Da Silva back to his place, erm, on the bench in the process.
I am not suggesting that DDG is the best keeper one can inspire to be. There's goalkeepers like Buffon for example who made VDS look like Taibi at Juventus. However he's an excellent goalkeeper who can serve us well up until we are in a position to replace him. The problem lie with our tactics. We play a high line with no DM to shield that, a LB that can't defend, a RB that can only defend (AWB) or can only attack (Dalot) and the slowest CB United had since Steve Bruce. That creates a huge gap between the back line and the goalkeeper that ANY goalkeeper would struggle with let alone an old fashioned type of goalkeeper such as DDG.