I think Ole has done a good job, but ultimately it reached a point where he had taken the team as far as he could. Jose left us in an absolute mess - he may have won some silverware, but it was at the cost of any semblance of long term potential. Ole came in and instilled the first bit of genuine positivity I have seen in the club since Fergie left. He revitalised the team, got them (at times) playing some great attacking football, cleared out some of the galacticos and instead built a team with a core around young English players, that will leave the next manager with a strong side to work with.
Having said all that, it became very clear - especially this season - that something was missing on the coaching and tactical side of things. The players looked lost, there was no particular effective system of play - you want a team to be more than the sum of its parts, ours was the opposite. I said that the board would give Ole until Christmas to turn things around, but the Watford result was simply too much, his position became very much untenable at that point, and it was the right decision to part ways.
I will remember Ole as the one who managed to bring back a bit of the 'old' United, who started building what will hopefully go on to be a successful winning squad, but who fell short on the coaching and tactical level. I still think he would be make a good DoF for us, when paired with a master tactician to sort out the day-to-day/match tactics.
Henderson, Maguire, AWB, Shaw, Sancho, Rashford, Greenwood - thats 7 English players who could form the core of our team over close to the next decade. It may not be fashionable to say this right now - but they (along with others in the squad such as McT and Donny) are good players, capable of a lot more than they have shown lately. We also have an abundance of quality youngsters coming through the system.
The job for the next manager is relatively simple - sort the midfield out, and get the players playing as a team. Ole's job when joining was a much harder one. I think he has left the club and the squad in a much better state than he took over, and he deserves credit for that.