This was always a problem I had with western comics, even if there were a number of graphic novels I bought and liked. It was one thing if the original writer wanted to move on and a new one stepped in to take over, but this tradition just kept going for decades, with mixed results. Sure, a whole mythos has been built with plenty to draw from for a number of adaptations, and there are plenty of good story arcs and one-shots, but it isn’t very good when creating a single, coherent narrative. You just get tons of retcons which render previous events meaningless and you’re wondering what exactly is the point of this hero’s journey when there’s no real end in sight.
There’s plenty of manga series which are far from perfect but most of them generally have a “beginning-middle-end” in mind.