1. It was announced at the beginning of the war.
2. True, but for the sake of their Captains bloodline and simply caring, just because they could have.
3. They could've gotten a small sailboat like Mihawk and sailed on over.
OP has a point. Except Shanks and Buggy. Really only Rayleigh imo.
Mihawk is a Shichi and he actually wanted to participate in the war.
1. Lmao, you expect everyone to make it in time from where ever they were? They're not just chilling near MF, they could be anywhere in the whole wide world. Gettin to MF isn't as easy as you think. They aren't gonna save some random pirate they don't know.
2. Thats not the point though. Why should the old and retired Roger pirates enter a war to rescue a kid who they don't even know? Ace is Whitebeard and his crews responsibility. Saving Ace was their job not Rayleigh's or anyone elses.
Shanks knew Ace personally so he had his reasons to enter and stop the war. He didn't fight, he simply ended it. Ace was freed but it was his own foolishness that caused his death.
You can't blame Rayleigh or Scopper for not joining the war. It wasn't their responsibility+they didn't know Roger had a son.
Even Garp can't be blamed. The moment Ace became a pirate was the moment he started making his own decisions as a man and became a criminal. You can't expect Garp to save him. He did what he could.