You don't think we improved the quality of the squad? Man just look at the team back then. We could have picked better upgrades I agree but how can you not give credit for at least starting the overhaul I don't get it. We were absolutely shambolic after LVG and Mourinho in both quality and mentality. How can you possibly put all the current problems on mismanagement of 2 years prior? We finished 3ed and 2ed ffs with a lot of players young and yet to reach their potential. The next manager has to build on that and add some extra quality. He wasn't good enough to take us all the way we all know that, but you make it sound like we were fighting relegation with the prime 2008 team
I am not sure why you are giving props to Ole's overhaul when he has created a situation that actually needs an overhaul again. Players wanting out, too many options in certain areas down to ill prioritisation of transfers, buying the wrong calibre of talent in CB/RB, etc. He did not do a good job in the overhaul - he spent a lot of money quite badly and I can only credit him for turfing out Lukaku and Sanchez.
You are comparing peaks of Ole to the troughs of the previous managers. I think if we evaluate Ole we should do so fairly (so that we can actually move on to Rangnick and put the Ole sub conversation to bed, if you don't mind).
Ole's peak was finishing 2nd with 74 points. This was off the back of a manager who peaked with the same team at around 81 points. Domestically Ole also achieved no finals of cups, so it's not unfair to say he failed to achieve heights of his predecessor and that too after being backed 150m+ on the squad beyond what he was given. His key sale was Lukaku but he brought in the likes of Telles, Cavani, Wan Bissaka, Maguire, VDB and Bruno and still failed to deliver domestic consistence that could be seen as an improvement on peak of the previous manager. That too after 2 years in the role and much money spent.
Also in his peak performance as manager he failed to win a cup and actually had a narrative of semi final/final voodoo about the players where the mentality was questioned. A mentality that was actually new because Mourinho took the squad to Europa Cup triumph in his first(?) or second season, I forgot which one. I would argue the players were undoubtedly happier with Ole, why wouldn't they be because he was so lackadaisical. But as a winning mentality? No I think that reduced in Ole's time compared to Mourinho's time.
Now for the troughs. I'll keep this short - I have never seen us fall so low as a club in performance, in calibre, in tactics and in game-plan as I did in Ole's final few months as manager. It was so astoundingly shocking, it's difficult to argue a worse time as a Manchester United supporter in the Premier League era. Even under Jose, it was toxic but the performances were never so bad to be embarrassed on the pitch by midtable/relegation fighting clubs and see records broken.
So to conclude - not a relegation fighting team. But a good squad capable of comfortable top 4 finish from a decent coach, which ultimately scrapped into top 4 in year 1. Did better in year 2, albeit comfortably worse than what a lesser squad was able to achieve not long before, and still 12 points off the leaders. Not what you expect from any decent coach when they're in the role for 2+ years. And then year 3? Well that was a shit show of epic proportion.
My gripe with Ole was that he never deserved the job, he was never consistent enough in performances (often outperforming XG in matches won for very long periods, 2 years into the role), he never fulfilled his promise about working harder as a team or pressing or organization, he never won cups and he never mustered a title race in 3.5 years. I didn't rate him at Cardiff, or as Interim as United manager and I don't rate him looking back. The only time I thought "oh he might be good actually" was for a brief spell in year 2 when he outperformed XG but it was always unsustainable. You can see the chaos and lack of structure still on the pitch. It's hard to argue he is a good manager after the above but if you think differently that's fine.
Moving on to Rangnick now - I fully accept results take time and performances too. But I see organization and structure. I see weaknesses in the high line which Brentford had exposed but the better we get at picking up new habits of quick interchange, better decision making and positional press triggers, the less we will see the silly mistakes. Klopp's Liverpool and Pep's City were very much the same in the early days and I obviously doubt we can get as far as they did in the end - however I know that top managers will take time to do a reset. So long as 1) they have some established pedigree in their philosophy, 2) they obviously know their vision inside out and have no problem communicating it and 3) can display performance improvements on a generally upward trajectory, I am pleased. And that's me parking results by the way - even if we looked at results I think we've done a good job so far under Rangnick. 1 or 2 slipups but that's palatable.