The issue really has nothing to do with luffy, it has to do with you, the reader, getting invested. Luffy doesn't care about any past history of any conflict, but it doesn't stop Oda anyway from delivering it before said conflict occurs. In this case, its the Void Century and we need to get invested in the WG losing after that, not beforehand and finding out later. It makes no sense narratively.
like i said , we are getting tiny crumbs abt history
the D and ancient weapons are alrdy revealed
what the onepiece has is basically something which is written abt imu being defeated
that will basically tell us how this entire ordeal will go
there will be no tension for the readers if they alrdy know how the final war will go
considering oden knew that kaido would have been defeated by new pirates , this entire fate is alrdy written in the onepiece .
we are slowly getting crumbs of the wolrd government being the evil organisation and what it did in the past , imu can easily reveal some of that like he alrdy did with the D mystery .
luffy's main trigger will simply just be rescuing vivi , he wont care abt something which happened centuries ago