First no need to go extreme, we have a wonderful squad but we have a relatively poor midfield when it is compared by other departments. Michael Carrick is our only central midfielder who would realistically go into the bench of Bayern and Barca, and I think those teams are the benchmark of today's midfield.
Second, we won the title last year but that do not change the fact that in many games we were overplayed and had more comebacks than in any other season in the history of Premier League. Those changes were most of the times from pure determination and from our strikers ability. Add to that, other clubs were pretty shit. City the main competitor couldn't win a single match in UCL, while everyone knew that Chelsea had zero chance to win the title. Both these teams have signed more competent managers, and while both have improved a bit their squad you never know with them, they can spend another 50m if they want. On the other side we have lost the best manager of all time.
Third, we do not know if Moyes can improvise as good as SAF. SAF was great and utilized the team perfectly that even with an average midfield we made a lot of success. We could have probably been better in Europe with a better midfield but that is for another debate. The big point is that can Moyes do well with only these midfielders we have?
So the point is that Thiago would have greatly improved us and although we don't like those clauses, I think that it would have been good if we allowed it if that was the difference between Thiago signing or not. Of course it could be that the club doesn't rate him that much which is something entirely different.