Two cups in two seasons is all the hard cold data you can muster?Ok.....here is more hard cold data for this season:
-shots conceded 667-only Sheffied were worse.
-conceded three or more goals in 15 games while scoring a meagre 57 goals and a negative GD( -1).
-finished bottom of a CL group that had Galatasaray and Copenhagen winning just one game and conceding 15(a record for epl teams) and eliminated from Europe before Christmas.
-total losses in all competions-19(in all MU history, more losses have only happened 9 times).
-beaten at Old Trafford 6 times( for context,in the first five premier league seasons combined MU lost six times at home).
The above is just casual research and I can finetune it if I delved deeper. I now await the usual cringeworthy justifications(injuries and dishonest medical team,structure,new way of playing,didn't understand new currency...and on and on). Of course no mention of the suicidal donut midfield formation and brain-dead subs in the dying minutes of games leading to loss of points.
With less stubborness and a pragmatic midfield formation that takes into account the injuries, the losses wouldn't have been so many.Therefore to answer your question, the poor season is 70% attributable to him. Even with the new structure who is to say his stubborness and poor in-game management will be better next season?And no one ignores the cup,we were all happy about it because we support the club,not the manager (how is that for balance?). However some of us refuse to be hoodwinked by just one game.