Interestingly enough most of the very greatest players to ever pick up the instrument played bolt-ons - I believe the the most important factor in any bass is the fingers that are playing it
Although I whole-heartedly agree that the player is the most important part of the equation, I have to disagree that the greatest players played bolt-ons - obviously many important players played Fenders - Donald Duck Dunn, Carol Kaye, Jaco Pastorius, to name a few - but I can think of a bunch of great bassists that didn't:
Paul McCartney - set neck Hofner, neck-through Rickenbacker
Jack Bruce - set neck Gibson EB-3
Chris Squire - neck-through Rickenbacker
Geddy Lee - neck-through Rickenbacker
Stanley Clarke - do I even need to say it?
Jack Casady, Phil Lesh - Alembic-modded Guilds (set neck), Alembics
So not really disagreeing, just wanted to give props to Rickenbacker, Gibson, and Alembic playing greats!