Rorsharch Is it somehow much harder to write a non system novel?
Nope. System novel is actually harder since the author need to 'design' the system. What feature would be unlocked next, etc.
It is easier to make cultivation novel, just give a cool name cultivation technique, where the MC is actually eating pill like popcorn or meditating in a cave for (insert super long time). Add some logic to make the cultivation sound good.
For example Moon Walking Divine Heaven Spiritual Technique, required the user to moonwalk to cultivate, and so on. Of course, I read a novel (Way of Choice?) which had very confusing cultivation, that even made me think that was real. Nevertheless, I forget (skip) those long and confusing sentences tho. That doesn't work in real life (and I better use the time to read mathematic book, that mathematic book is work in real life.), and anything write about cultivation is actually word counts fillers (the same with System Ding! Ding! Ding! Ding!). That is word count fillers.
Also, System novel needs to 'keep' track the Lv, mission, point, and blablabla. So it is harder. LitRPG is even harder since status windows is the key.
Nevertheless, the main factor is people love System. Actually the trending topic is "sex' or erotica.
This showed that you rarely check Original.
Another reason why System novel is popular perhaps because it is easier to know about the novel even just by reading the title.
Between "Arrogant Young Master System" or "Endless Universes". Which one would you click to read?
The only reason, this Rabbink can't write my novel title with system was that it was even confusing for me, the Author. Is it a system?
PS: Most critics to System novel is the authors often forget to use system after Volume 1. It became non-system.