What I don't understand is people automatically assuming Ney staying meant more CL titles. It's a possibility but not very likely. We had a younger/stronger Messi (who scored 50 goals in 16/17) and a younger Ney and still got clapped away from home by the likes of City, PSG, and Juve. They both stepped in each other's way that season IMO with less than efficient styles of play.
If you tell me we could have kept 14/15 or even first half of 15/16 Ney all these years, we win the 18/19 CL for sure and maybe even the 17/18 one. But the player he is today can't coexist with Messi IMO. It's one or the other.
And as you saw before Mbappe came on, Ney can't do it by himself either (creating + scoring). So, we'd need to find an explosive, vertical forward to complement his game style if we built around him instead of Messi. Ironically enough, Messi would benefit from this too.