When something isn't working and you don't have a plan B logically you try something else till you get it right or find some sort of balance. I think we have all seen the United line up this season and we all collectively sighed (especially against Olympiakos) at the some of the names on team sheet. Valencia, Young, and Cleverley aren't love by most at the moment but they have had the odd good game but are far from the best players we have.
Tactically from what we have seen this season Moyes likes to play the ball down the wing (which is what Valencia and Young are good at), and that works (sometimes) and would be a decent starting point if we were at the start of the season. As the season goes on most coaches evolve the style and "philosophy' of their teams. Anchelotti is a good example, when he arrived at Real Madrid he used the 4-2-3-1 that Mourinho operated because at the time it was what the players were used to and sometimes changing things too quickly unsettles players. It worked for a period but he wasn't getting the best out of Benzema, he tried Ronaldo in that position in pre-season but he didn't seem to enjoy the role (Bale also played in that position a couple of times). The solution that he came up with was to change the formation, he switched to a 4-3-3 and its working but that is because Benzema is not a conventional striker, to get the best out of him Anchelotti removed the #10 position allowing Benzema to drop deep and use his creative ability which allows Ronlado and Bale to make use of the space he creates when he displaces defenders as well as leading the line in attack.
David Moyes in comparison has stuck to his guns (DOWN THE WING LADS!!), with the right players that can work but we don't have a six plus foot striker who can redirect Valencia or Young's aimless crosses into the goal. He (Moyes) has in attack and in midfield Rooney, Mata, Van Persie, Kagawa, Nani, Carrick, Fletcher, Fellaini (who in my opinion has not had enough game time to warrant some of the criticism he has gotten) and Januzaj who are all more than comfortable with the ball at their feet, they know how to make and find space, make use of other players making runs, and can operate as alternating pivots to give us variation going forward . As a manager you would want to use that kind of talent in a system that suits their ability, is functional, efficient, effective, and that the players and fans would enjoy. Instead of adapting to suit the kind of players he has acquired and inherited Moyes is trying to force them into a system that they haven't responded to and the inconsistency in results and player form has been the end product.
The solution in our case would be for Moyes to sit his players and staff down (if he hasn't already) and ask the players what type of football they want to play, its all well and good being a bold leader dictating proceedings from aloft but time for pettiness and power struggles has long since past and its time for the Moyes (if he wants to save his job) to adopt and enact progressive tactics and measures.