This is where you're talking nonsense. How do you build on that team exactly? Which big player is going to accept being the new james or the new morata exactly? The problem is that 16/17 was the end of the cycle for that team. The CL last season was a lucky fluke. We needed to make big changes, particularly to a midfield that was never particularly well assembled, but worked as a great platform for marcelo and carvajal to dominate the wings, with the box presence of Cristiano+Benzema/Bale to mame it effective. If we don't occupy the box with multiple strikers and don't get penetration from the wings, that midfield trio becomes good for keeping and recycling the ball, and little else.
There was a recent article from el pais which claimed apparently Zidane wanted to sell the BBC, Isco, Modric and Lucas, and make big changes to the team, with only ramos, varane, marcelo, dani, casemiro and kroos considered untouchable. And he quit because Perez disagreed with that.