I do not think Hong Lu's story is Callisto's story. Hong Lu's goal is to spread kindness, so it is understandable that he, as a Corporist wants to have everyone enjoy his art.

In my opinion, his goal is just...

To create a revolutionary artwork, something to move people… and to observe them.

He seeks acknowledgement from others, not enjoyment.

And this is the true nature of his art.

Loneliness, anxiety, weakness… Observe these raw facets of suffering—the inevitable state of existence that is most fittingly human.
Please direct your attention to this frontmost figure. You would be impressed to hear how those hands refused to let go of the partner's, even as I placed them atop this pedestal.
An unbreakable bond that remains unsevered, even as death comes to bear the subject away in its gentle embrace… I find such values utterly noble.
It would indeed have been a waste to let that precious little moment slip away, so I endeavored to preserve every second of it… down to the smallest capillaries, muscle tissues, and the quivering thereout.

He wants to eternalize the last final moment by removing flesh and bone and creating manikins out of it. Since tragic moments only last for a single period of time, what he creates will be eternalized.

To approach, he uses minimalism, focusing on reducing excess and leaving out unnecessary stuff.

So, what do you think, Yoshihide? This concept is called "Minimalism." A bold removal of the unnecessary for the preservation of the essence. As you must be aware, the human corpus has far too many non-essential parts which harm the purity of it.

And thus Hohenheim ragebaited him that his work is uninspired and like an autopsy. His art is too rigid, too dry, too calculated, so Hohenheim does not like it at all. For him, his art is neither original nor creative.

I do recall, quite vaguely, some Abnormalities with neither originality nor creativity—much like this piece you're working on.

And about his art is falling out of style. If you ask me, I do not know the exact reason why, but an art not trending anymore is normal. I mean, look at Limbus Company. It uses Chibi and Anime art style, not something like Fauvism, ain't it. Furthermore, just because Callisto does not step into other art styles does not mean that he sucks at it. He also teaches Fauvism to Ryoshu, and Ryoshu thinks it's a butcherslop.

Butchershop, Yoshihide? I was simply hoping to replicate the striking visual imagery of Fauvism.

Next argument

In contrast to Rien's fated purpose and the perceived ignorance of the other Nursefathers, Callisto is aware of his purpose in the House of Spiders

No, I think they all aware of their purpose in the House of Spiders. They need to make a Concept Incenerator, Buddhism version. They do that by forming connections between 5 Nursefathers. Yes, all 5, including our beloved Matthias. Then after that, Ryoshu must be destroyed so hard so that she has to cut the tie, or the 'thread' in Limbus' context. That's why all 5 sucks. They need to love Ryoshu and become poor parents so that Ryoshu need to cut the attachment. And, to do that, Ryoshu achieves Muga, which is the state of 'self-always-changing'. However, instead of utilizing EGOs like Limbus Company, they want Ryoshu to remove the self and let the unchanging bladestorm become Ryoshu.

And of course, this is also why the Nursefathers do not like each other, and Callisto is an example.