No way this masterpiece got axed meanwhile repulsive media like "gUsHiNg OvEr MaGiCaL gIrLs" is allowed to exist. These are the symptoms of a hypocritical society.
This manga was about the length it should have been? I know, there are many, many manga that will inflate to 500+ chapters if they can, but I really kind of hate those. I'd much rather have a 30-60ish chapters manga that tells its story then has a very satisfying ending like this and then the mangaka moves on to the next thing. Of course we don't know what was going on at the publisher, but this sure feels like what the author actually wanted to do.
Kawamura-sensei has enough good stuff going on that I don't think he needs to stretch a series out to infinity. Rather, there should be way more series ending way sooner. I think this was a huge creative success, no tears need to be shed.
So I think your point would be much better made as 'Why is this manga ending in a timely satisfying manner when One Piece still is going on
decades after Oda wanted to end it?' Which is pretty much a rhetorical question, we know why, but it's way more pertinent.