Compared to Moyes teams? Where United were breaking records left and right. He had inherited a team capable of attacking football and turned them into a mid table defensive pressing unit incapable of being able to string chances together. The only promising things were when he played Januzai out wide and he was able to take on a man. Moyes' teams would go on and not be able to create anything some games, that was far more frustrating than shots on goal stats.
The points difference isn't really an issue either because at least there are some big factors in why United dropped points earlier on in the season. Southampton home loss isn't something to be flippant about either, Southampton played fucking fantastic. You won't see many better defensive away displays than that, they have a genuine chance in remaining in the top 5. Even then, when United started playing directly in a 'Plan B' scenario Mata could have had a hattrick. Still, 0 shots on target but chances matter more.
United can't even use the preferred formation at the moment. It'll take a bit of explaining:
Earlier on, injuries really played their part at the back (with starting the league on a LDDWL). Even the new defensive signings got injured, so, its going to take a while before that back line has the experience to play solidly. One of the main complaints from fans is that LvG is continuing to use a 3-5-2 formation - but I see it as one of those necessary evils. They simply can't afford to have a weak centreback partnership who also lack cover of a full time right/left back. Rafael's out every month and Shaw is probably due another injury next week! At the moment, the 3-5-2 is a smart way to adapt for poor individual defencive players - a back 4 of Valencia/Smalling/McNair/Blackett might be one of the biggest jokes of the league. 3-5-2 adapts for players who trip over themselves with always an extra man to cover you, always a spare person to press on an opponent. Even then, they still managed to screw it up royally in one of the very few times Southampton attempted to get forward with more than 2 players, with 4 players being attracted to the ball and Blackett losing his man. They kept losing Sterling earlier on versus Liverpool as well, but hey at least United could have scored 5 goals going forward.
The next problem is that with your defenders in this system they need to be good passers of the ball. Or as my Dutch friend calls it bluntly, footballers. Possession is built from the back- you have 5 players and a goal keeper to utilize even if being pressed by the opponents forwards, there should still be spaces and passing angles open to use in this system. There isn't an extra man in the midfield to choose from, every midfielder will be marked. Players like Evans is completely inept in being able to pass the ball out of the defence: last week at Yeovil he completely struggled to do anything but put the ball out of touch if he saw someone running towards him after receiving the ball. It's no wonder to see he's dropped this week in favour of Danny Blind. And it's no surprise to see Koeman after the match state "You analyse your opponents. You know they have difficulties building up with three centre-backs."
Unfortunately, as I said in the previous paragraph, I don't think switching to a 4-2-2-2 would be the better solution until they buy better defenders or the current ones step up. Whilst it would allow the build up play to be done with better ball players (Carrick/Blind/Herrera), the risks of goals conceded might be too high. If they indeed buy a top footballing defender, maybe they'll even stick with 3-5-2 or go with wider players depending on what striker is available in a 3-4-3 or 4-3-3. We still don't know what LvG wants to achieve as his end goal strategy thanks to all these problems. He's just had to make do what what he's had.
And finally, the last 3rd & 4th attacking areas. Yesterday was strange with Di Maria up front as a choice over Falcao, something something 'tactical' LvG said- we'll never know. Rooney in the CM/CAM role is also quite troubling as he's pretty hit and miss; he attempted quite a few Scholes styled passes and none of them came off. Di Maria played where Rooney did earlier on in the season to good effect, whilst Rooney is naturally a striker. It's a strange situation, maybe one of the few times I'm a bit baffled to LvG's choices - alongside his continual omission of Herrera. I have to assume Di Maria is not just right physically yet or 'match fit'. So, in time, United will have him back in the middle and he'll wreak more havoc. United indeed lost a creative midfielder when he got injured and it's hurt the attacking chances, shots on goal etc.
tldr= Moyes teams performances were far worse last season. Utd suffer far too many injuries earlier on to explain some stupid points dropped (Leicester?). Now have a tighter defence than before thanks to a back 3, and hopefully buy actual footballers who can ramp up the possession/build up play. Di Maria will return to the middle and Rooney will be forced off to the front or replace Mata (etc all interchangeable), whilst other players have returned to fitness (Falcao, who we've only seen like 20% of his potential).