Lame display..? Think you might want to watch the game again. United had 16 attempts on goal with 6 on target. First half we had something like 48% possession and exactly the same attempts on goal with the exact same number on target. The second half we had more possession and more attempts on goal. Like I said the first half was pretty even and United dominated the second half.
As for the substitutions, they all worked pretty well imo.
I'm quite happy that Van Gaal is giving our young players a chance.