Imo, when it comes to Shanks/BB, these are things he won't avoid.
For sure, a lot of what I currently call One Piece's "second act" (Hody, Caesar, Doflamingo, Katakuri, Big Mom, and Kaido) are a very weird time for the series. 5 of the 6 villains weren't really set up prior to the timeskip, save for Doflamingo (who I felt was the most fleshed out one).
Now as we head to what Im considering his 3rd act and probably his "biggest" Saga, I personally don't see him short changing Shanks, Blackbeard, Dragon, Kuma, Admirals, WG, etc, because all of these characters are from the earlier parts of the series. For sure, things like Weevil or Im or Rocks are newer concepts, but I think they all have implications to currently existing characters anyway.
Vegapunk is practically an exception, because he's been referenced since Water 7 and seems to have his hands in basically every single major arc since (Mentioned in Thriller Bark, Sabaody, Marineford, Punk Hazard, Dressrosa, WCI, and Wano).
Idk I'm pretty confident that Oda won't flunk out on what are presumably his favorite characters (we already know this is the case for Shanks and Buggy). A lot of this is just pure DNA for the endgame anyway, however many arcs there are left.
LMAO dude, be prepared...
Just to say a few things here:
We got the underworld brokers "presentations" in the shadows watching an experiment from Caesar Clown, then one of the editor's notes for these chapters was: "Everyone is watching!".
Later on, Oda or his editor(s) said that Punk Hazard is part of Wano... but we never get anything of these ones anymore, like if this part of the manga did never exists. Like convenience for cutting of/ripping off characters and plots.
We had the emperors of the underworld at WCI, at least 5 of them, Du Feld, Drug Peclo, Giberson and Umit, but it seems that there are even more (see Jinbe's speech and silhouettes on his back), well, we never have heard about them anymore, again like if Oda just wanted to rip them off from the story.
So, now who two Yonko, the two most veterans besides Whitebeard, have been defeated, WE DO NOT EVEN SEE THEM GETTING PISSED AT THEIR DEFEAT!
Dude, the underworld is tied to Yonko, Shichibukai, Kings, Nobles and even the World Government but nothing, we get nothing. Nothing happened here. It's suppossed to be in chaos right now.
The Strawhats and Law have fucked up the underworld too many times, and this time has been the fatal blow because two Yonko have been blown up! They have lost almost all, like trades, money, experiments...
SUSPICIOUS AS FUCK, and all of this stuff is gonna be rushed somehow.