City were also relatively direct last season.
The CL is a much higher level than the PL. In Europe you are facing one of the top 1-4 teams in a leading European league. Domestically, 80% of your games come against teams outside of the CL spots which is what the assessment of our players is largely based off.
To give a rudimentary analogy, if most domestic teams are of a beginner or intermediate level of difficulty, the European knockout ties are advanced difficulty especially because of the technical proficiency of European teams.
Furthermore, the higher level of difficulty will lead to more nerves, more mistakes, and will expose more weaknesses. It's simply a higher level of testing our players are going through.
We also face CL level teams in England but they have different styles to European teams and aren't as good technically. We also improved our performance against our top 4 domestic competitors through repeated exposure. This team will only improve in Europe through repeated exposure to knockout football.
Arsene's Arsenal didn't pass the quarter finals of the CL until 9 years into his reign. Ferguson's Man Utd didn't reach the final until over a decade after he took over. Abramovic's Chelsea also took a similar length of time. Mansour's Man City took even longer. It's a completely different beast.