I think to some extent the reason it looks desperate is principally because after two managers have come and failed, we are desperate. But some of it is about Mourinho personally as well: there is a perception, whether accurate or not, that he was passed over for the job before, that we snubbed him, but now we are going back to him cap in hand. That looks desperate, and sometimes appearances are as important as realities. There is also the perception among some people - a few, a lot, I dont know - that he may be past it, that he lost the plot in Madrid, it got worse at Chelsea, he finally crashed and burned, but that we turned to him anyway as our last roll of the dice. That looks like desperation. There is the view, this one more mainstream, that we would have appointed other people if we had the chance - Guardiola, Ancelotti, Klopp, whoever, but all those candidates slipped through our fingers: that looks desperate.
It can be argued both ways of course, I dont need to repeat the accepted wisdom that he is a serial winner, PL tested, wants to manage us more than he has ever wanted anything in his life before, wants to replicate SAF etc etc. So in that sense it doesnt look desperate.
But among my friends who dont support United the word desperate is cropping up a lot to describe this, and to be honest I am not inclined to disagree, and that is related to the very first bit of this post: whether this appointment is desperate specifically because it is Mourinho or not, the fact of the matter is we are now desperate, desperate for an end to the shit we have endured ever since SAF left, desperately hoping Mourinho will be our saviour. So whether or not people are using the word to mean the same thing, I do think it is a fair description of where we are right now, so I am not inclined to argue the point.
