I don't understand people who complain about flashbacks.
Go watch Boruto if you want only action and nothing more.
I am waiting for secrets being revealed. I don't even want One Piece to be finished in 5 years ;(
This is a false dichotomy, first of all.
Second, flashbacks can be good, average or bad. This one has never been brilliant and has heavily relied on characters who aren't Oden, but at this point it is just a clumsy succession of events lacking in terms of proper writing.
I mean, Oda had all the ingredients to narrate the last events in Oden's life mimicking an oden recipe and he chose the most boring, easiest to write outcome. That has no merit at all, it's even anticlimatic. He could have created a new "Brook's death" like climax but hasn't been smart enough to do so. He's basically copying here and there from Japanese history and folklore with zero inspiration.
This flashback has been a mess from day one. You could literally tell most of what we've seen just from reading the manga and knowing some basic Japanese history.