You are mistaken optimism for realism. Friend used to give me one good advice, always judge situations based on present. Never on the future and even more importantly, on the past. Past can't teach you anything new. Future we cannot know, but in present, we have both past and future. Present is realism, fact, firm ground. Take a look what has United done this season, how they look at this moment. You have every right to be afraid for its future, but looking at the present, United has done pretty good job. And it will get better. Got a world class manager who's best trait is to get the players to their maximum, he has great record with molding youngsters and is a born winner. He came with something different, new philosophy that's working. Even if United doesn't sign anyone, there are no reason why this squad shouldn't be in CL next year. Having Fellaini and Cleverley as 5th and 6th option is anything but bad. They are not bad players, both can and will be useful, I'm positive. Squad depth in defense is thin, that's why United is pursuing players like Benatia or Blind (examples, I don't know Uniteds targets). Not only to give quality, but also depth.
Have faith, there is time and place for panic, middle of August isn't one.