I agree that another season before this one, showing a bit of the missing years, would have been good.
The flashbacks ended up serving a purpose more than just showing us how Nucky came up & it all came full circle in the end. I do think it was a nice little twist, but it somehow felt off. We have not seen little Tommy in quite some time & things have come a long way since Jimmy getting killed- that it all felt out of place a bit.
We knew how things were going to end up historically with Luciano, Capone, etc. - But the ride along the way is in part what made this show great. Now we came to the end after jumping ahead a few years & it all felt very rushed & pushed aside. I get that the final season focus was on Nucky & that is all well and good, but big parts of the series had us in the mix with the gangster situations. I feel like Winter said "Oh, well you know what happens here, so we will skip all that".
In the end, this really was a story about Nucky & the others were not the stars, but merely a cast of characters. If they would have done some flashbacks throughout the series, the full circle ending may have hit home harder. I still enjoyed the ending, but wish we would have had a few more episodes on the road there.