Please excuse any grammar roosterups.
Hugo was injured and recovered.
All of them are of a good footballing standard but are very up and down performance-wise, it's all very normal. Mourinho has improved them but looks to be very short term, look where we are now.
All manager should "improve" players "performance-wise" on a day to day period, these players were excellent 'at times' under Poch, yes but not all the time, I agree.
There are very few managers that "improve" players in the long term. Klopp ATM would be top IMHO with the likes of Salad etc
Bottom line if they are all improved why do they all look so poor?
As an aside, Ndombele looked like a very troubled and agitated young man before he got "injured" and headed off at Brighton.