In this instance, Mourinho's comments are fair, I think.
Ndombele simply isn't trying. He cannot be relied upon. Man has incredible talent but zero application - in training or during games. Compare and contrast to an equally talented player in Gio Lo Celso who works his bollocks off every game.
The video in the link, which you've probably seen before, is typical of what we get from Ndombele whenever we're not in possession. He's simply not interested. Bear in mind that he had only come on to the pitch 5 minutes earlier. It's simply unacceptable for a player earning £200K per week. It's nothing less than an insult to the fans who pay his wages while earning little more than a tenth of that per annum.
https://twitter.com/i/web/status/1234273891721383937
Mourinho has tried the kid gloves treatment with no change of attitude by Ndombele. What he said after the game yesterday might appear to be the nuclear option but it might also be the only option he has left. Let's hope it works, because there is an outstanding player in there if Ndombele chooses to apply himself.