I think we must take three things into consideration.
The first one is that this year's top 4 has been really poor, Chelsea, Leicester and us wouldnt be getting the top 4 in a "normal" season. If we win our next two matches we will end up with 68 points, with that amout of points we would end up 6th in a "normal" season. Last season we finished 6th with 66 points and got only 2 points in lour last 5 games for comparison purposes. So judging Ole on getting top 4 seems unfair and achieving only that shouldnt be enough at all.
The second one is that since overall we didnt make any substancial improvement points wise, we should ask ourselves do we improved in performances? I would say this season was pretty much as the one before. Two "different" teams overall, the first part of the season was pretty much the same as the last part of last season, poor performances and we seemed to regresse. The second part of the season was pretty much as the hooneymoon part with Ole. Great results for a sustained period, everything seemed to click, high expectations, etc. So do we think Ole can maintain the team performing as this? or is it just a patch as the other ones?
Finally we must consider that we are against probably the most competitive teams in premier league history, the last two seasons have required around 100 points to be champions, we are 30-35 points again from that, do we think Ole has that kind of potential?
I think we must get a another manager, of course the last performances have been better but overall I dont think Ole has the potential to get us to the very top in order to beat Pep and Klopp we need a manager that revolutions the game like they did before. Pochetinno is available so its the perfect time to be in form him rather than let him join another team and then realize Ole is not up to it and have to look around for a manager when all the "great" ones are taken.
We've seen how this team can perform with the starting XI, players such as Pogba, Bruno, Greenwood, Martial, Rashford can offer really exciting offensive power. I can only imagine how good can they perform if coached properly. Not anything against Ole, but I think the lift in form has more to do with Bruno's arrival and a morale lift rather than his tactics actually comming together.
Ole for all the good, and bad, work he's done cant show a sustained playing style if he doesnt have all the starting XI available. That makes me think the performances are more due to the quality of the players rather than the system he is implementing. Of course a team can only perform to a certain level without quality players, but the really great managers make a team better than the sum of their parts.