Plenty of them can realize their dreams without Luffy. Zoro just needs to grow his strength until he fights Mihawk. Usopp can be brave warrior of the sea by joining any decent crew or even form his own. Chopper can become a brilliant doctor without even sailing the sea if he choose to do that any decent crew would be enough. Nami could do the same to draw map of the world becoming a marine like her mother would also allow her to pursue her dream. Brook just wants to see Laboon again, so that leaves Robin Sanji and Franky who would depend on Luffy to achieve their goals. It's Luffy who heavily depends on his crew to achieve his dream
They would all need to be all around able people to do it
by themselves
NOne of them are navigators (except for Nami) so they ain't going anywhere except by chance.
None of them are doctors (except for Chopper) so they die pretty soon from illness.
Only one of them can read poneglyphs, which you need to fullfil a couple of dreams (draw a world map, become PK, learn true history)
Only one of them is s cook, though that doesn't mean the others wouldn't survive still
Only one of them is a shipwright meaning the others can't fix their boats and will get stranded/die
Musician isn't really important as a role on a ship and you can survive in the OP world without music
All in all, achieving their dreams is a group effort, not something an individual can do due to their own ability