We had two moments that greatly hindered the club's evolution.
The first happened in 2010, after winning the EPL, the management didn't know how to renew the squad and we lost the 10/11 championship because of that, since United was weak that year.
It continued in 2011/2012 and culminated with the club's weakest campaign in years, but we had a miracle of winning the Champions League.
In 2017 our slump began with a horrible transfer market and we are still paying for that mistake today.
Buying Morata and losing Costa had a lot of impact, as well as losing Matic and buying Bakayoko.
We missed the UCL that year and the following year we had for example to buy Kepa because Alisson wanted a club that would play in the UCL and went to Liverpool (we are still looking for a goalkeeper today).
Despite so many breakdowns and it hurt to lose so many cup finals, the club once again managed without anticipation to win another Champions League, which helped boost the club's status. However, we again failed to buy Lukaku and many of the signings were poor
Spending so much money on Havertz and Werner proved to be a failure, like so many others (the worst last year was cucurella).
On the other hand, City is really strong and it will be difficult to win the Premierleague again.
It could be years before we win the title again unfortunately.