I agree with you. And Man City comeback happened two seasons ago, when they started poorly, but slowly improved and continued their consistent run to the title. While they were certainly poor last season, it's still too early to judge City's performance as a slump.
So even if Man City starts poorly, their rivals shouldn't underestimate their strength under Pep Guardiola. They could bounce back midway through the season and rediscover their best form. City's current form is understandable, especially with the departures of several key players and the addition of new players who have made the team unorganized due to Pep's constant changes in composition and strategy. So even though Man City is currently in decline, Liverpool, Arsenal, and Chelsea must still be wary of a Man City revival.
One this I want people should know is that manchester City struggle right now should not be taken as a permanent problem. Because We have seen this before, two seasons ago they started badly, but luckily enough Pep Guardiola fixed things and they went on a strong run by winning the title. Even last season, despite some weak moments, Manchester City prove to us that a slow start does not always decide their season.
This season looks more like a period of change to them. Some important players have left the team and the new signings are still trying to fit in the clubs. Pep Guardiola normally changes in tactics and lineups which have also made the team less stable. This has made Manchester City look weaker, but history shows that once Pep Guardiola find the right balance, they usually become very hard to stop in the season