We're seeing play out in real time the importance of squad dynamics and profile over just accumulation of talent with no cohesive plan. On its own, I'm entirely fine with stacking talent, but Madrid brought in Mbappé the same summer that they lost Kroos, Joselu, and Nacho. I'm not going to litigate about that, all three wanted to leave for their own reasons, Madrid isn't to blame there. The problems are entirely in how they've reacted. Joselu scored 18 goals last season, they very obviously replaced that number and then some with Mbappé, but they didn't replace his profile at all. They don't have an aerial threat on crosses and they don't have someone with that natural strikers' instinct. You generally want to force teams to defend more facets of attack, but there is no team in the world that has to gameplan for Madrid's aerial game, it doesn't exist. Their way of replacing Kroos has been giving nearly-40-year-old Luka Modric more playing time than he had a year ago. They don't have a playmaking mid (that Ancelotti trusts) anywhere else in the team. Their way of replacing Nacho was [404 centerback not found].
This isn't even touching on the problems created by Mbappé and Vini both preferring to operate from the same areas on the field, and now having to adapt off each other, it doesn't touch on that you now have two players who generally aren't much involved in the defensive work whereas last year it was only Vini who was given license to stay further forward, and it doesn't touch on the star player dynamics of handling the glamor things like who gets PK duty and the chance to pad their goal stats.
There is the part of me that thinks it would be foolish gamble that Mbappé's career profile will flop at Madrid. He signed a five year contract. I remember when Modric had a disappointing first season there, shit, even CR7's "worst" season in terms of goal scoring at Madrid was in his first season. He's proven too much throughout his career previously to be written off anytime soon, he's earned the benefit of more time. He could still come good in time. At the same time...regrettably, I find myself writing about Madrid a lot on the internet and have developed a lot of opinions about them, and one of them that I said a lot during the summer was that they had about as bad a transfer window as they could've had where one of things they did was "sign Kylian Mbappé". Lots of people were skeptical about that claim at the time, but we're 2.5 months into the season and I only feel further emboldened in my stance now. I've seen nothing to tell me I was wrong.