I'll be a voice of cautious dissent.
I think it is kind of a playstyle thing, but being inflexible and locked-in is part of the "fun failure" of the Wizard class. It emphasizes that this is a class about advanced preparation and specific solutions. A wizard caught with her pants down, in a chaotic situation she wasn't ready for,
should get screwed. On the other side, when things go according to plan, she should have just the right tools for the specific jobs she needs accomplished.
That needn't be true for every single spellcaster, but it should be true for the academic wizard archetype in my games. Flexibility is not a virtue, it leads to a class I'm not as interested in playing. If I wanted flexibility, I'd go with a different spellcaster, or a different class altogether.
This is not the most awful compromise, but honestly the 5e wizard is currently really something I'm not personally that interested in playing because of the great sum of ways that it breaks the binary play experience I'm looking for in a wizard. I get why, but if that binary play experience isn't available within 5e's wizard class, I won't really be interested in it.
But I wasn't interested in 4e's wizard class in part for the same reason, so another edition without a core wizard I like isn't going to ruin the whole game for me, necessarily.

ESPECIALLY if the flexibility and modularity of the game allow me to make a more binary wizard, I have no qualms with a more flexible, open, constant-magic kind of baseline. I'd only really have a problem if I didn't have an option for doing other stuff.