Our current trouble stems from the inability of those who created this 2020-21 squad to predict how will this team perform.
Indeed, this fiasco is a consequence of many decisions over the last 4-5 years, but the last two nails in the coffin were put this summer when we went after Pirlo and Arthur/McKennie. I'm not sure which of the two was a bigger mistake, because they are connected. Even another coach would have failed with this squad. Not this royally, but failed nonetheless. And even with a better midfield, Pirlo would have failed. Though, no Pirlo or Pirlo+better midfield would have at least guaranteed top 4.
But I'd still go for the midfield selection as the greatest mistake. And this is where the Arthur purchase can be described as disastrous. The guys in charge didn't predict that with Rabiot, Bentancur, and Ramsey we needed to buy two different kinds of midfielders (or of much better quality), or, which is worse imo, they thought Arthur is the guy to complement Rabiot and co. and make things work in midfield. That was a huge miss. McKennie himself is not a terrible buy, but it is in the context.
tl/dr all our troubles are 99% fault of the management. So it's a question of whether we will trust the management to fix the mess they single-handedly created, or we should simply change these guys with new folks.