Sophomore slump: why is Netflix losing so many viewers for second seasons?
Netflix
(www.theguardian.com)
This is a problem of Netflix's own creation. Long gaps between seasons of on-going series followed by cancelation a without conclusions drive most viewers to stick to "limited series". At this point, "limited series" and self contained seasons (think Apple's Slow Horses) are the only format they should follow.
I think Apple does it best with Slow Horses where at the end of the last episode of the season, they preview the next season which has already begun production.