Ole was a mess. Under him discipline went to the dogs (injured players going to Dubai, agents speaking out of turn etc), his coaching team couldn't figure out how to tackle persistent issues like defending/scoring from set pieces while the club invested 415m without any form of return in terms of trophies. In terms of the squad he left a very unbalanced squad filled with players who are either ill suited for the modern game or have a weak mentality.
Let's dissect the team bit by bit
GK: He left a side with too many GKs. DDG is a top goalkeeper and the most highly paid one at the moment. Henderson is among the top 10 most paid goalkeepers in the world, Heaton can do a job as an EPL goalkeeper and only god knows why on earth Grant is still here. That could only cause friction in the dressing room as only one goalkeeper can play per game
DEF: He left a defence that is unsuited for modern football. Maguire is too slow for a high line, AWB offers nothing going forward which is acceptable for a late 80s RB but not for a modern FB, Telles can attack but he can't defend, Varane is good but there are question marks on whether he can remain fit and Shaw gives like 6 months of good football every 6 years.
DM: The only DM we've got is Matic whose 33. God knows why Ole never tackled that
B2B: We've got 2 and they aren't particularly good (McT and Fred)
No 10: We've got Pogba, VDB, Bruno, Lingard and Mata. WTF he was thinking hording so many no 10s? Couldn't he see a problem in having so many no 10s?
Flanks: We were told that the RW was a position we really needed to spend money upon. Ole's administration bought 3 and he barely played them. Sancho and Diallo were barely ever played while Pellistri was sent on loan. That's around 100m worth of talent.
STK: Ole saw no issues having a 36 year old and a 34 year old leading our line in an increasingly fast paced and defensive EPL