Real Madrid have a great squad line up now and any coach that gets to manage this squad well will win more big m records to their names and their achievements will be much in a short time. The repetition of the Champions Legaue Trophy three times in a row can be replicated by Real Madrid again with this kind of squad they’ve put together.
I Definitely disagree with your view that a very good squad doesn’t need a good coach and just any manager can manage them and get success from them. We have seen many great teams of individual brilliance and without a tactically sound coach they end up winning nothing. I can remember the country Belgium falling into this category when there so called generational talents couldn’t winning anything. At club side we can use the same Real Madrid as a case study they had a galatico squad with many of the worlds greats around 2007-2010 and rare win anything and not until they hire Jose Mourinho after then, they started scooping some trophies and also came Carlo Ancelloti who did the same.
After their departure the coin already had the BBC frontline which would have won everything under just any coach but under Rafa Benitez they struggle not until Zidane came and won the treble in the champions league from the same team that Benitez struggled with. So there certainly a need for a technical coach even more so for star studded teams like the currently Madrid