Details like this make classes unique and interesting without radical changes to the DMs world.
No, it depends on the setting and what is appropriate
I can come up with a dozen concepts of trained assassins that not cutthroats and don't involve an assassin's guild. Some of them might be tied an organizations, but others are not.
In my campaign setting, barbarian does not = rage. The raging barbarian as the basis for a class, officially, began in 3e. While, the raging barbarian is found in one or two cultures, I draw my inspiration from 1e in which rage was not a feature and the barbarian comes from one of several cultures that determined the remaining starting weapons and provided extra tertiary "skills" Additional, influence comes from the 2e Fighter kits in the Complete Fighter's and additional kits in the Complete barbarian's handbook .
In my 3e campaign, this translates, to the Unearhed Arcana Barbarian hunter variant with variant weapon styles based upon culture, cultural based weapon groups (see Unearthed Arcana Weapon Groups) and the Unearthed Arcana favored environment replacement for favored enemy.
And, while there are barbarians that rage, then there are the raging "barbarians" from more civilized lands. Urban Barbarians growing up in the back alleys and pubs of slum districts using rage and toughness (they trade out wilderness skills for urban based and lose trap sense in exchange for other features) as well as few nobles that fly into violent rages abandoning technique for fury
Rangers in my current campaign may or may not be organizationally based. Those that are organizationally based include warrior priests of a nature god (they get a bard's spell progression), Robin Hood like nobles leading peasants including 3e Unearthed Arcana wilderness rogues in revolt against a usurper (they get no spells, but rather bonus feats when they would get spells). The remainder are various wilderness types described by some of the kits in the 2e Complete Ranger's Handbook and don't cast spells. The one thing that they all have in common are being light armor warriors (using 3e armor categories), survival and stealth.
Paladins in my current campaign are organization based. They are an all male religious sect serving a single deity (the females are a variant of the OA Shaman).
In another campaign, they were not organization based. They were simply individual religiously devout good warriors good upholding ideals of virtue, purity and goodness and being rewarded by one of the good deities.
Next needs to give me the tools to duplicate all of these without assuming story elements or organizational ties. If it can't, it fails from perspective.