I didn't say never, but not for centuries, and most of the changes have been either cosmetic, or for minor changes in tone. No where near the same as people asking for different necks, bridges, pickups, number of strings, etc. as with basses
The violin emerged from instruments like the lira da braccio and the lira da gamba (viol da gamba). There were fretted viols. The first depiction of a violin had three strings. The fingerboard changed lengths over time as well as its orientation. Scale length changed. String tension changed. The method of attaching the neck changed. The actual strings used changed. Mechanical amplification has been introduced. Electric violins were invested. You can now get five string violins.
Literally everything you listed: different necks, bridges (I’m sure those have developed over time), “pickups” (substitute how the sound projection occurs), number of strings, etc. has changed.
I think you’re failing to appreciate just how much innovation has occurred, and that’s just of the items we know about - it doesn’t include failed attempts along the way that never made it outside of workshops.
And this was without modern technology and tools.
Seriously, you’re really doing a disservice to the history of musical instruments.