Well, you are right for sure, but you are also making this look or sound like it's now they Manchester city started losing match, aleast I know that since this season began, they've not been in their best form just as they were during last two seasons which saw them going home with the premier league title.
They indeed need a total overhaul of players but this can only be done in the summer in preparation for another season, because even if they can do the overhauling now, it's already too late for them as they may likely not make it to the top anymore.
Every team will go through a golden era then back to basic mode all the best teams in the world must have experienced it and now it's Manchester City turn, so it's true they have to start from the beginning and prepare new talents but yeah there is no guarantee they can do it. We can see examples of some teams like Chelsea who have missed many seasons or Arsenal who always finish in 2nd place even though it can be said that Arsenal is in a golden era it's just that there are other teams that are better.
For next season I think Liverpool will experience it I mean missing the golden era, what we see this season will not be the same as next season and maybe we will see the same situation like Manchester City this season. The first indication for Liverpool is if Mo Salah moves, because so far he has not extended his contract and his contract will end this season, from several sources said he wants to move to the Saudi Pro League but yeah we will wait for the full news in the next transfer window.