Van Gaal, speaking in his first English media interview of United's tour of the USA, denied the idea that succeeding Moyes would be easier than following Sir Alex Ferguson, who won 13 titles in 26 years at Old Trafford.
In Van Gaal's eyes, Ferguson left Moyes with a team of winners. He says he is inheriting a "broken" squad awash with attacking midfielders.
"No," Van Gaal said when asked whether following Ferguson would have been harder.
"I don't agree. I had to follow Bobby Robson at Barcelona the year after he won three titles and there wasn't a problem (Van Gaal won the league that year).
"When there is success you have a very good squad, and now I have to follow and the squad was broken I think.
"When you look at the squad, there is quality. There is (Wayne) Rooney, (Robin) van Persie, (Javier) Hernandez, (Danny) Welbeck, but you also see Juan Mata, (Marouane) Fellaini, and you see (Ander) Herrera. There are a lot of players that can play in the same position.
"It is not in balance. It's more difficult to succeed in a difficult situation than in a fantastic situation."
Van Gaal will look to address the imbalance in his squad by signing at least two players over the next three weeks.
United have been told they will have to stump up £79 million to sign other target Kevin Strootman from Roma while Real Madrid are also demanding a big fee for Angel Di Maria, who is also on the club's radar.
Van Gaal insists he will not pay over the odds for any transfer targets though.
"I don't buy players for the sake of buying players," he said. "I buy players to improve my selection.
"Now I don't know if we will play (5-3-2) or 4-3-3. If I play 4-3-3 I need more specialists in the wings and attackers and then we have to buy another kind of player."
Meanwhile, Van Gaal insists he will not get drawn into any mind-games with Jose Mourinho this season and he says he still regards the Chelsea manager as his "friend".
Mourinho said had Chelsea paid that kind of money to the 19-year-old, it would have "killed" the London club.
United boss Van Gaal hinted he would speak privately to Mourinho about the matter. Many saw that as a sign the two former colleagues were set for a rocky relationship this season.
Mourinho, who worked as Van Gaal's assistant at Barcelona for three years, has a record of trying to wind up fellow managers.
But Van Gaal is sure he will have a harmonious relationship with the Portuguese this term even though both he and his former protege are in charge of teams vying for the title.
"I don't think I will fall out with him. He is my friend," Van Gaal said of Mourinho.
United play the third game of their tour against Inter Milan in Washington DC on Tuesday night.
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