Me and a friend have been saying the Scabbards replaced the SHs this arc and took their screentime/roles. We waited years IRL for them to reunite after being split up so much and now they are the side characters in this arc and the Scabbards are the MCs. Oda really wanted to do his own version of Seven Samurai or something.
I said to my friend the SHs should have replaced the Scabbards in the present, inherited their wills and played the roles of them, fighting for their cause and avenging them.
At least if nothing else, as you said, they should have stopped being relevant after fighting Kaido and failing to avenge Oden. Denjiro hasn't even done anything so far and been missing for about a year IRL!
I do kinda like the Scabbards but I hate that the SHs are being replaced by them and suffering in screentime for it. But given how Oda is writing Usopp and Nami, it's kind of a blessing too I guess.