I really don't think that's a fair take on The Leftovers. It was adapted from a novel, which season 1 follows the plot of pretty closely and completely. The remaining two seasons are entirely new plot but iirc the author was involved.

The novel doesn't resolve the core mystery. I won't spoil whether the show does, but it's kind of beside the point anyway. One of the core themes is how people grapple with sudden loss, something beyond their control, something unknowable. In any case the show resolves itself with a satisfying amount of closure in three seasons. Much fewer open threads and plot holes than LOST. The unresolved aspects of The Leftovers are genuinely thought-provoking and deep.

I wholly agree with Wikipedia's summary: "The first season received mostly positive reviews. However, the second and third seasons were highly acclaimed, with many critics referring to The Leftovers as one of the greatest television series of all time, with particular praise for its writing, directing, acting (particularly Theroux’s and Coon's) and thematic depth."

You say "The finale comes only when there's no more money to be made" ... that doesn't jive with a final season having a 99% on Rotten Tomatoes and 98% on Metacritic!