Agree with most of this, but i also think that you're letting them for some of their actions off the hook way too easily. I don't mind them believing that they deserved someone better than Mourinho, Solskjaer or even Rangnick (who was never going to stay as manager) to train them. I won't hold it against them if, in private conversations, they feel that the club should have targeted other players in the summer (e.g. the rumours that Ronnie came in and stirred the dynamics both in the dressing room and the first team). It may not always be normal, but it is certainly expected in any working environment when things aren't going as planned.
But some of them are definitely playing their part in this. And, in the end, it's not Rangnick they're hurting, but the club itself. This is what most fans have a problem with. I don't know about you, but Shaw's "lack of love" at United rubbed me up the wrong way. Because he is shitting on the club. A club that has done, and continues doing, lots of mistakes that hinder its footballing operations. But, nevertheless, a club that stood by his side during the darkest period of his career. Such was/is the belief that he would become the next Irwin/Evra for us, that we still haven't signed a left back that can seriously make the spot his by challenging Shaw. Similarly, when Rashford hints to mismanagement by Solskjaer, you can't say that there's not a case to made there. But the way he carries himself on the pitch, doing his own thing and looking disinterested, shows someone who believes he's too important for the United brand. All this talk about how he wants a new contract or else... Jesus Christ. Can you blame people for believing that all the leaks/SM posting will simply vanish if he's offered Sancho's wages?
And that's just two of them. You can add Lingard posting with a WHU shirt or Raiola blaming United for everything and claiming that Pogba is basically doing us a favour by staying. The list is endless. It's one thing just giving it your best and failing. But when you know you're doing all you can, you're usually OK with yourself and you don't need to create all this drama just to tell the world: "Look, it's not my fault". What we have here is closer to an office full of well-paid employees, most of which have been promoted way beyond their qualifications, and now that the company is going to the gutter, they only care about shifting the blame and saving face. It's not entirely their fault, but, this isn't just any company. It's an organization that millions of people around the world love and are emotionally invested in.
The strict disciplinarian will not last a single season, if the high echelons don't agree that wholesome changes are needed in the first team. The mentality of the club has to change because it's the club itself that has made many of these players believe that they are the dog's bollocks and that they can either say or insinuate anything they want in the media.
We need the progressive and good manager to identify 2-3 quality signings in positions that will make the team better and what we need even more is a good structure that will give him the opportunity to sign the right players who will hit the ground running.
When we'll look again like a team that's going places, even if we can't challenge right away, the noise will go away. They are making a fuss right now because they like their fat pay checks and they can easily hide their weaknesses/failings behind the club's current predicament. The only way we can fix that is by moving forward, not with a rod. Create an attacking trident similar to the Ronaldo/Tevez/Rooney one without Rashford, and see whether the latter's performances pick up or not. But to do that you don't need Roy Keane, you need a good manager and intermediates that will convince the board that this is the way forward.
