Your point is negated by the fact you didnt see all the stuff from season 3-6 that did show they knew where they were going.
In fact there are elements of season two that only make sence after seeing season 5 and 6.
Sure, they might not have had every single line of dialogue and every character locked down, and they had to change a few things due to actors being better/worse/being a shit behind scenes/drunk driving, but overall the big stuff was there all along.
The show got progressivly more sci fi from the 3rd series onwards, I think if you had stuck with it you might be giving a different answer now.
No, I understand that the show had sci-fi elements, and that they were constantly trumped up as being important, but, from everything I know, those elements were nothing more than diversions from the Jacob/MiB faith-science struggle thing. Sure, they spent a season time travelling, but at the end, they blow up a nuke, come back to 2007, and, that's it. Time travel didn't matter to the overarching plot or the mystery of the Island, it was a thing the characters did for a season. Same for DHARMA - at the end of the day, their role in the plot was, what, a red herring for a season or two, and then "some scientists investigated the Island - they found that it was weird," but they didn't play a role in the final season, really.
The Lost writers were very good at introducing new plot lines all the time that would dazzle you, but so few of them were actually necessary to the narrative they wanted to build. You loved the show where you get wild misdirection that keeps you on your toes every other episode, and, yes, it's about the characters and all that good stuff, but it just wasn't the show
I wanted to watch.