If Luffy never existed, would all of the other Straw Hat Pirates be dead?

 

Most likely. Without Luffy-

Theres nobody to stop Morgan from executing Zoro.

Kuro kills Usopp and all of Syrup Village.

Kreig takes over the Baratie and kills Sanji when he gets in the way.

Wapol returns to Drum Island and kills Chopper, Kureha, and Dalton for opposing him.

Crocodile destroys Alubarna, assassinates Vivi, and when the Poneglyph doesn’t reveal Pluton, he kills Robin.

CP9 kidnaps Franky for the Pluton blueprints and kills him afterwards to keep him quiet.

The only ones with a chance are Nami, Brooke, and Jimbei, and honestly they aren’t all that much better off.

If Nami gets away from Buggy, she’ll still be stuck as a slave to Arlong for the rest of her life.

Brooke had survived for quite a while without his shadow, but he’s still stranded alone in the Florian triangle avoiding the sun forever.

Jimbei might be able to defeat Hody Jones and his crew, but he’s still forced to serve Big Mom.

So you know, not exactly living their best lives.

Sanji might actually have the best chance of anyone. Kreig hadn’t done all that much damage when Mihawk showed up, and without Zoro there to satisfy his boredom, he would probably finish slaughtering Krieg’s armada (which is, you know, kind of his job as a warlord, taking out other pirates to protect civilians).

And Jimbei might actually die in Impel Down well before Hody Jones made his move. If he were still in level six and BlackBeard made it there (he might not if he still encountered Magellan, since without Luffy there’s no mass breakout happening, so Shiryu wouldn’t be released to save Teach from Magellan’s poison. Then again, without Luffy’s breakout to quell, Magellan might not attack the warlord Teach so hastily, if at all) he would almost certainly be killed, either in the free for all Teach incited for the right to join his crew, or afterward because Teach knows Jimbei is loyal to Whitebeard.