The entire comment was phrased as a fact but sure, lets go off on the technicality that the post mentioned "I" in multiple places.
It also doesn't help that the logic used in that comment is what you see used on Twitter by people who want to downplay Kimetsu's success all the damn time.
Lastly - I don't care about Kimetsu. I haven't read it past the Mugen train arc. So if people forget about it tomorrow, I won't bat an eye. But it's pretty shortsighted to think that something THIS popular, breaking records not just in the manga industry but multiple other entertainment industries as well won't have a major lasting legacy. It's a big cultural hit like Kimetsu that can often shift industries to new trends.
Cult? What? Lol. What a weird word to use on a manga forum.
It is not a technicality, it is how opinion are phrased. Just before there are haters on twitter or other social media, it does not mean that everyone else is. You disagree? Fine, it did not write a message on a discussion forum to have people tell me that I am right. Since most of thread is dedicated to sales, I wanted to propose a different point of discussion.
First of all, we all agree that KnY has and will have a big cultural impact in Japan for merchandise, volumes purchased by a wide variety of people and acknowledged by many various people outside the manga/anime world.
But, I think you missed the fact that I was not talking about Japan. I was referring to the legacy in other parts of the world. Naturally, I am biased towards a Europe-centric point of view. However, I feel that the anime arrived "too late" to create long-lasting forums about the manga. Death Note was an exception with a quite unique concept, supported by the anime in this.
I wish the same to KnY, but I am not sure.
Unlike you, I have read all the manga chapters and and I found it a good read.
However, it follows a similar pattern used for series like Black Cat and Samurai Deeper Kyo, where the first part is more focussed on the characters themselves, but it quickly becomes a series of battles against the group of the final villain.
To me, it seems the story is quite self-contained as it is. Unfortunately, I do not think a sequel would be easy to write as most of the characters would need to replaced and some of elements of the original story could be there anymore.
It is respectable that the manga was not prolonged just because of the success, but I feel a few more little arcs in the middle of the series would have helped people enjoying and care about many characters even more.
If you want, I would say that KnY's story feels like a fairytale rather than a novel, an epic or a series of short stories.
As for the legacy, once again, I think that with the manga already finished, there was not enough time to create long-lasting communities online. "Our" dedicated forum is already dead, unfortunately, just one year or so after the first episode of the anime.
I believe most of its legacy will come from the beautiful anime adaptation which can inspire other studios. In this sense, it may have a long-lasting impact on the worldwide anime community.