Indeed. There is simply no role for Fellaini at the club. He's poor as a holding midfielder, not much better in a box-to-box capacity and useful to certain teams as a target man. Unfortunately, United aren't the latter, so he really cannot offer anything here.
He's probably the first team midfielder I'd like to see leave the most - Anderson aside. Much-maligned Cleverley doesn't have the ceiling to become a starting midfielder for us and he is a very limited player without even one outstanding quality, but at least he is a player who is a befitting of van Gaal's philosophy when high on confidence and in form. I do think LVG can revitalise him to some degree.
As far as I'm concerned, Carrick's place at the club is untouchable, despite having a disappointing season because he is by far our best midfielder. I don't expect him to be a starting midfielder for us next season, but the fact our midfield will vastly improve should benefit him greatly if we aren't so dependent on him. I don't believe it's the realms of possibility to perform near the standard he set when we won the title.
And with Fletcher, his energy and work-rate has unfortunately diminished due to his illness, but he could still prove more adept than Fellaini for the holding midfield role if partnered correctly. Plus, we could still receive a fee in excess of £10M for Fellaini. Leaving sentimentality out of the equation, Fletcher wouldn't fetch for much. Even just selling Fellaini to recoup some money would be worth it, because our outlay is inevitably going to be sky-high come September.