Not sure the shininess of GJ has worn off for anyone, but, here we are without him and, despite having Aguero, we are missing game-winning sitters regularly and have one of the worst shots-to-goals ratios in the league.
As Pep said, you can't imagine we wouldn't have beaten Liverpool quite comfortably if GJ was on the park, but that's not always going to be a gimme, nor is his form.
Aguero's decline in front of goal this year should come as a warning to City going forward. I can't imagine they will gamble on a return to form for Kun/Kelechi and a free-from-injuries Jesus when they will have access to almost unlimited resources to assemble the best squad for Pep available.
I see no issue with wanting a player like Mbappe regardless.