Season 1s are great, setup, some payoff, a bit of lead into the overarching story. Then season 2 to X. The heroes win and then lose in the final episode, cliffhanger to next season. People get bored. Final season is announced and they wrap up the show.
I think the point of the question is that the producers get greedy midway. And stop the progress so they can go indefinitely. Then when the show is cancelled the finish the story arcs in the final season.
I don’t think it’s the producers–it’s the networks or streaming service. I’ve read a lot of articles where a showrunner says they had a 4 year plan or a one season plan, only to have the show be really popular and additional seasons added, or the opposite which we’ve all encountered, the show cancelled before the plan plays out.
I don’t know how to get around this but I would love to see a model where more shows follow a short run K drama type schedule and get a fixed 8 or 16 or 32 episodes to tell their story, and that’s it. That way, they can plan ahead of time without having to worry about network interference. Obviously this would never fly with U.S. broadcast networks but they’re a dying breed anyway.