That is true, it's not the same situation and it's not entirely comparable. But there is an issue with discussion here, which is sometimes people don't want to compare United to anyone.
If you bring up top level continental clubs changing managers mid-season and getting instant results, the comparison is dismissed because those clubs had much better squads from the outset. If you bring up lower level clubs changing managers mid-season and getting instant results, the comparison is dismissed because those clubs have different objectives. That leaves us with other PL clubs who changed managers mid-season to overhaul their team, like Liverpool (Klopp) and Arsenal (Arteta). But what tends to happen is that when the comparison reflects poorly on the United manager, the differences (squad/position/etc.) are once again used to argue that the comparison can't be fully made.
The end result is that people are asked to trust a mode of operation that is largely unprecedented in modern football and that cannot be compared to anything. Obviously some people will be very skeptical of that.
I would say the United situation is almost unique in world football right now.
1. United have been incredibly poorly run for the last decade or so. In years to come, University business schools will use United as a cade study for how NOT to run a business. I am deadly serious on that.
2. United don't necessarily have a squad of poor players but they do have a squad completely unsuited to competing in the Premier League. Lack of physicality, lack of legs and a large number of very young and inexperienced players. It's crazy to imagine that a club of United's stature are fielding an attack week-in, week-out led by Rasmus Hojlund and Alejandro Garnacho. That amounts to gross negligence. Can you point to another club in world football that is supposedly meant to be competing at the top of the table that contains 6 regular starters who are 23 or under? Sometimes 7 or 8?
3. Despite the above, it's still treated as a surprise when United don't win football matches. The expectation is that United will beat teams like Bournemouth, Forest and Wolves, despite there being really no basis to believe this based on results over the last 12-18 months.
4. There has been a huge amount of upheaval and chaos behind the scenes, culminating in the recent takeover which has led to personnel changes across every department and a complete change in strategy on and off the field.
I would argue that you can't compare this to Klopp walking into Liverpool or Arteta walking into Arsenal. This is a much, much bigger rebuild. It's almost uniquely big.
+ in any case, why do we need to compare with other teams and other managers? I can see with my own two eyes what the problems are, what is going well and what is not going well - and so can Amorim. None of them can be fixed overnight and some simply require new players, and a new profile of player.
At a very, very basic level we had two major problems pre-INEOS / Amorim. The culture and talent identification. The culture was one of excess, of player power, of throwing money away, of greed, of laziness and underperformance.
The players being identified to come into the club were completely the wrong profile. Ageing superstars looking for one last big contract or doddery technicians with no legs personally identified by EtH to compound our pre-existing issues with physicality.
You can't change culture or the physical profile of the squad overnight. It'll take time.