well i wouldnt call it a waste of time. we have learned how wano progressed through 20 years. orochis past. odens past. roger finding the one piece. some history on roger and whitebeard and some other small things. so a waste of time isnt really appropriate here
We didn't learn how Wano progressed through 20 years. Theres a time skip. We are already back grown the flashback
The time we COULD'VE learned more already bout wano was MONTAGED with Oden collecting the Scabbards in one panel each and then he left Wano and then he came back and died.
The Roger and whitebeard stuff can only not be a waste of time to me if they come back this arc. Like rayleigh or gaban or Marco and co come to wano this arc.
See what I think is a waste of time is when things are happening and they don't affect that current story that much. Opening the borders doesn't matter more from this flashback, the Scabbards don't matter more, Hiyori and momo don't matter more.
The most relevant thing we've gotten is that Luffy is the chosen one and Orochi is a psychopath bent on destroying the country. And I only sort of care about the Orochi part.