It's one of the worst arcs in all of one piece and easily the worst post time skip arc.
It's the best arc to remake because they can fix how terrible the pacing is. They still can't make Hody a compelling villain, or bring any level of stakes to the arc.
The poison was obviously a ruse. Everything we know about Shanks points to him never using such tactics.
Barto fucked up and he had to a pay a price for it, the price he paid was far better than the one Kid got. They'll show up later in the Mr. Nika-go or something.
Shanks absolutely knows...
Their immortality and overwhelming haki make them stronger than their physical ability. Not that they aren't insanely strong. Luffy would have beaten all five of them if they didn't regenerate. Hell even Zoro clashes with one of them.
Current Luffy could beat all of them at once (Blackbeard was never a supernova).
Wano showed pretty convincingly the massive power difference between Zoro, Luffy, and the other nine supernovas.
Minus Uruge, we still don't have a clue about him.