Planning ahead is in the DNA of the Wizard. You have to make choices what to prepare based on what you know and predict about your immediate future.
What needs to happen is Long Rest being more restricted than it is in patch 5 so those choices carry weight.
Then, if you don't like those restrictions and playing a thinking Intelligence based class >> Sorcerer is for you with fun spontaneous casting and cool heritage.
Strong class identity is what makes a class based system fun in the first place. If you start blending abilities and playstyles of different classes, you might as well start cutting entire classes from the game.
