Lost represented the triumph of appealing characters and fine acting over an incoherent story. What kept me coming back for six seasons certainly wasn't the multitude of never-explained mysteries or the numerous plot-lines that were dropped by the writers like hot potatoes. If this had been a written work, rather than television, I would have abandoned it long ago, and I suspect most of the audience would have done likewise. As a visual medium, it revolved around the people. Lost had a large cast of well-chosen actors and they sold this unhinged, rudderless story. Long after I had given up hope that the writers knew what they were doing, or that the story would make a lick of sense, I kept watching. As the end of the series approached the question became: how bad would this train-wreck be?
Lost should be a case study in why a room full of writers should not be asked to produce long-form narrative. If Lost had been episodic, with discrete hour-long stories, no problem. Whoever had the initial vision for the show -- J.J. Abrams presumably -- apparently left the writers on their own sometime during the first season ("See ya, losers!"), and the writers were left to tread water ever since. Lost is what happens when a story is written by committee.
Compare other television series: Twin Peaks or Buffy the Vampire Slayer, which represented the singular vision of their creators. Love them or hate them, those two shows are examples of originality and strong creative leadership. Lost had no such integrity, no guiding vision.
The final season was especially disappointing, focused as it was on the simplistic good versus evil story of Jacob and the smoke monster, yin versus yang, light versus dark, weighed down with heavy amounts of Christian imagery. After seasons with more interesting conflicts, to end up where the story did was both trite and dull. Where were the days when Jack and Locke argued about the guiding principles of faith and science? When was Ben, easily the most compelling antagonist the show had to offer, last actually a factor in the story? As a substitute for Ben, the smoke monster was not nearly as interesting. When were the mysteries of the island last intriguing and dangerous? When did the show last have a sense of humor? Not during the last season.
The self-indulgent final episode had its entertaining moments and its howlers. This wasn't an ending to a six-season show, this was a six-year cast reunion. The number of tearfully reunited friends and romantic couples was taken to such an extreme that it became self-parody. In the end it was a series that overstayed its welcome, undercutting what was once enjoyable about the show and diminishing the series as a whole.
Related post: Lost in the Writers' Room