I think Netflix should give every series one season. At the end of the season, producers and writers have a chance to pitch to Netflix the number of seasons that they want. A final determination is made, and it is not changed. Writers have a target ending to shoot for, fans know what to expect.
It all depends on the story. ATLA (Avatar: the last airbender) is a great example for something that needs a contract for multiple seasons from the start: they knew they'll have 3 seasons, and that was one big arc and storyline. Same for Trollhunters; it was unfortunate to only have 1 season for the third installation, Wizards: it was way to fast.
Other series, however... are dead slow. It was delightful to recently watch a 1998 film, `Ronin`: 2 hours, and more story happened, than in 2 seasons of most series.
Isn't the biggest problem that writers don't have a clear destination in mind for the series? And so it wanders aimlessly. That's exactly the problem I think this would solve.
