Part of the issue I think is the conflating of the performance of individual players in the squad with the performance of the squad as a whole. The two very much feed in to each other, but they aren't exactly the same thing. I agree that our team's form "has gone off a cliff-edge", but this can very much be a result of many of the individual players passing their peaks/reaching their tipping points at the same time. As I mentioned with the case of Liverpool, when you have a critical mass of players arriving at their peak ages at a similar time it can have an amplifier effect and generate a winning momentum. But also this continued high level of performance can be exhausting and is not sustainable indefinitely. Hence, once all of these key players have suddenly started tipping over to the downward part of their slope and their bodies start catching up with them this momentum can be lost quickly and there can be a negative amplifier effect on the team. For some of the players not fully at the wall yet then after a sufficient break they could maybe get back to almost where they were at their peak for a bit longer, but that would require a sufficient amount of new energy and motivation brought in to the squad from enough new players coming up to their peaks. Due to being passed their peak they are no longer in a position where they can generate the same momentum again themselves. This is why Ferguson talks about the four-year cycle of teams and things needing to be sufficiently refreshed at the end of these cycles. Our squad hit a similar tipping point/end of cycle early last year as Liverpool hit early this year. Many of the individuals passed their peak at a similar time and this had an amplifier effect but in halting momentum. At this point players can also experience the effects of their previous years of exertions suddenly catch up with them and their bodies. What was a well-oiled machine suddenly becomes fragmented and in need of being put back together again and given fresh impetus.
