Although Man United performance isn't as people's expected, they have no reason to drop to the relegation zone. Man United is still a big team, they have many skilled and quality players. They only have a problem with the mentality (motivation) and the strategy in playing, so they need a special coach to encourage the players' performance. Sure, it may be impossible to bring back the performance as in the Ferguson era. But they need to improve their current performance to be more competitive in EPL competition. If they cannot improve it, they will never win EPL title for sure.
Mate, nothing is impossible for Manchester United to return to the peak of its glory like in the Ferguson era. They have to be backed by strong finances to get there, have a lot of good and quality players and also a great management and coach as well. Who says Manchester City can win 4 Premier League titles in the last 5 seasons without strong financial backing? It's very unlikely, but because they have enough money to invest in good and quality players then Manchester City can do it now.
The same thing can be achieved by Manchester United especially if handled by the right people. Having good and quality players is a factor that will support improving the quality and mentality of the team to achieve the success it deserves. Now Manchester United don't have all that, so they have to start thinking about changing it if they still want to win titles.