Really it just retroactively hurt the show overall there is something about trying to rewatch it knowing there are no answers coming or are so stupid. I honestly expected the writers to tie everything together but instead they just gave up.
At this point my desire to rewatch the series is solely to refresh my memory and find out where I think it went wrong for me. I haven't seen most of the episodes since the original airing, so I don't recall where most of anything took place, but I do know my problems with it go back farther than s6.
As exciting as the "we have to go back to the island" flashforward was at the end of s3(?) was, as time went on I became more and more confused by why they all felt they had to go back. And how they did it, with the need to duplicate the original flight and passengers, didn't made a lot of sense. But at each step I never got too angry, because I understood they were holding some cards back to reveal later*. Of particular interest to me were Desmond's capabilities, which I imagined would help fix/explain things at some point in the game, but that really fizzled out.
There was a moment, (again it's been too long for me to place this properly, but I'm thinking around the s3/4), where they reveal the plane under the water on the news and Farraday is overcome with a deep sadness and he doesn't know why. I thought this moment was powerful and had sort of a David Lynchian feel. I don't recall that this ever amounted to anything though.
I guess I was really hoping the more sci-fi aspects of the show would be able to make a great finale. Time travel would be involved, I figured. And I assumed the s6 sideways universe really was an alternate/parallel universe caused by the s5 explosion, and that Desmond with his unique abilities would be able to straddle the universes and help them rejoin or something.
*I can only speak for myself, but the reason I expected things to be explained more is that throughout the series there were plenty of "that really makes no sense but i know there's more to be revealed so I will withhold judgment for now" moments. S1 in general was an exception, and there were characters here and there at times also, but for the most part the characters served the plot for the duration of the show. So no, with the show we got, I'm not up for a 'satisfying character finale.' It's the reason I want to go back and watch, I suppose: to find out if all those times I cut the show some slack because I knew not everything had been revealed outweigh the good stuff.
I certainly watched the show and eagerly anticipated most of it, but with the resolution we got I would classify it as one of the most frustrating shows I have ever watched.
Although the pilot episode(s) is probably the best start a show has ever had.