I skimmed over this a bit since there are a lot of posts here, but I don't think this was said yet. I was actually just thinking about this last night at 3am when I couldn't fall asleep. lol More precisely, I was thinking more about the Shounen Jump formula and the pitfalls of the comics they select for publication. I do believe in the it factor, but what is the it factor exactly?
I believe it is finding what an audience NEEDS. It's more than just a good story and art, though those things are important too. But oftentimes, and this includes my own comic, the story is a well thought out story, but is it what the audience NEEDS? For example, Dr Stone is doing really well right now and I've seen it get some good feedback. I read an interview with either the author or artist who said "We came up with this story in two weeks." In TWO WEEKS they came up with a story that was an instant success and now even has an anime adaption. When there are manga in the same magazine that the artists will work on and rework and rework for months, if not years, that flop after 19-30 chapters.
I often find they have something in common which is, while they may have interesting characters and a well written story, it just doesn't have the factor of being something the audience needs. Or there's the opposite issue, they do have something the audience needs but then they can't find a good author/artist for it. If anyone's been keeping up with WSJ, they're now on their THIRD attempt to do a shogi manga. They have recognized the audience's need for a good shogi manga, but none of them have anything else the audience needs. So yeah, sometimes what the audience needs isn't enough, but if you can find it and if you can write/draw it well, then I do think you can get in.
The thing with Dr Stone is that it's fulfilling this gap for a solid shounen science-focused manga at a time when people are getting more and more passionate about science. There was a need for this kind of manga. Then I look at Samurai 8 which I have found to be a very well written story, solid characters, really strong world building in it, but it doesn't seem to have the need factor in it. If it can find a need factor in it, it can really push forward.
YuGiOh is another great example, probably the best example. The first number of chapters didn't do well for the series. It was just about a random game every chapter. Then it had the card game chapter which was an instant success. Because there was a need for a card game manga when I don't think there really were any? And the manga is a really great formula because they were able to throw different games out there to the audience until the audience found one they really resonated with. The trouble is most of us webcomic artists don't have the time to throw out a new game idea every week to find one people like.
That's also why one shots are great. Relatively low time investment and able to throw out a bunch of ideas and see which ones stick.
I think art and a solid story are important, there are definitely comics out there that have the popularity because the art is world class amazing and the story is good. But when your art is good and not world class (like my own) then it's important to have that need factor (which I don't have aaahhhh).