Marketing and distribution can cost as much as the movie. For movies like this one, distributors want to see it before writing checks. They saw it, nobody wanted to write checks. Hence the old phrase "straight to video".
You pitch this movie as man against the elements, you cite the artistic success of Redford's "Jeremiah Johnson" and maybe Tom Hanks in "Cast Away", you show around a script which is a showcase for one veteran/mature/old famous actor, and so completely committed to him that there's no woman or other character or even a talking fish. Everybody scratches their head--but at least the budget is low. Well, who've you got lined up to play the guy? Robert Redford. It'll be an academy award performance.
All such projects are approved on hope. But movies are the death of hope, because success is not about hope but about execution, and execution is some combination of luck, talent and the alignment of mysterious spheres. Even great execution and story and a successful novel a the basis doesn't guarantee success. The classic illustration is The Great Santini, which became a critical darling but couldn't get a distributor and wound up making its debut on airplane screens.
The specific yachting "howlers" in "All is Lost" don't matter much to most viewers, but they do undermine interest by introducing confusion.
The bizarre story elements introduce further confusion by questioninig anybody's logical assumptions about sea stories. You can be wrecked in a flat calm? When climbing on deck in a storm you don;t close the sliding hatch after you? YOu can repair the hole in your hull with the complete West System Catalog on board, but are otherwise helpless to stop leaks? You can be easily rolled 360 degrees in a typical gale? YOur energies, when thousand miles from nowhere, should be directed to calling for help instead of pumping?
It's easy to question Redford's performance, which seems to be intentionally , let's say, stoical. That was probably his choice, and it probably seemed brave. But think of anyone else in the role, from Brad Pitt to Tommy Lee Jones, and ask what they could have done? Not much more, because there's just not much there. Not even a volley ball to talk to. Not even an ongoing voice-over of log book entries to expand on the visuals (except for a pathetic introduction narrative which is just a lugubrious mistake).
So, and all you are getting from me here is industry analysis and carping and "we're smarter than that", it all comes down, distribution-wire, to whether anybody thinks anybody will go see this turkey, and nobody thought anybody would, and so the prophecy becomes self-fulfilling.
We have a right to be offended by such a stupid movie, though, since it's about a world we care about, and they didn;t just get it wrong, they took all the drama out--and we know there is ample drama in the events chosen to be depicted, and they didn't bother to understand why or have the skill to show us how.