It's not about being "Bad" or "Good" developers, it's about Amateurs vs Professionals.
Professionals have a proper plan and know the overall progress and health of their project....
They don't just do whatever and hope for the best.
You would be surprised. It takes years of experience to become a "professional" to the level you are expecting.
A lot of first time "entrepreneurs" are flying by the seats of their pants and finding out what works and what doesn't. Hell, a lot of any small business first couple years is throwing shit against the wall and seeing what sticks.
Again, there are a lot of small businesses that don't make it out of their first year for a reason. Of the ones that register and are trackable, about 20% fail in first year, and 50% in first five. This includes people starting up businesses who are first timers as well as serial entrepreneurs and established business leaders.
That doesn't count the Aunts and Uncles with their small side gigs and hobbyist activities such as "professional photographer" and "website designer"... or "adult game 'Indie' developer."
You are applying your definition on something that is not actually the case in most instances.
A cliff hanger doesn't mean plot threads weren't resolved in the volume or that there were no climaxes in them.
If every book was cliff hangers nobody would buy any books.
He didn't say every book.
There are books with unresolved plots and there are books with resolution.
The Harry Potter series resolved short term tension and plot, but left long term tension and conflict open for many books in the series.
Heck, then there are the books of an author all set in the same universe... Such as Stephen King's.
Then there are the Robot, Empire, Foundation novels of Asimov.