@criver You are misunderstanding some things. RNG machines also have creativity in a sense. They just don't know whats good, thats literally the only difference. A human makes up a story and knows if its good or not, or at least as a human can understand humans enough to know what humans think is good. The AI is simply not there yet so it makes nonsense.
Not all humans can produce something "original" since the idea of originality is relative like pretty much everything else in existence. Game of Thrones is very big and popular but its not particularly original. LOTR too. A story does not have to be original to be good. These stories are just as original as something like Demon Slayer or most other manga. I have read enough to know that nothing is really "original" and thats its more about something being distinct. A story that is distinct is seen as more original even if it uses all the same elements. You can use all the same block to make the same basic thing and still have one be clearly better in people eyes than the other.
These Isekai are fun by default which makes them more desirable than other stories which are less default fun. You can write a vaguely interesting Isekai and it will by virtue of its Isekai qualities be better than its vaguely interesting competition. Some stories are just superior given the audience viewing them. So people make the one with better base stats and secure success. If you have a story to tell it is likely worth telling because it comes from within you. If your just constructing a product however there are plenty of ways to min/max your build to get the result you want.
People churn out garbage all the time. They also copy and tweak existing things. Rom-coms are notoriously the same damn story but they are super popular with certain demographics and thus get made to death. Trends shift and change but certain things are forever a part of humanity. You also do not need to be the MOST popular, you just need to be good enough. That gets you an ongoing story or "success" from a business standpoint. A true creative will toil more than most can imagine to create something special, even then it might not be popular. A person who makes plates is not the same as a person who makes designer plates. There is a big difference between creative and simple creation. Two people write stories. One is trying to get a best seller and make money, earn a living etc. The other just wants to write stories and hopes to earn a living to fund the writing of stories. The difference in priorities often has a huge impact on what kind of writing they do.
I also do not have enough Isekai to read. So its not like there is a problem with something being basically the same story. There are a million minor variations of this particular story and if you enjoy this kind of story you will likely enjoy the same story but a little different. I mean the MCU was not original at all. People loved that. You will find that being too original makes people uncomfortable and they may even lose interest if you don't hit the very effective beats that every other story does. MHA has gotten its success not by being super original but by being the story we all love honed to near perfection. There are issues but it generally hits all the beats when it comes to a story like itself.
I can watch almost any show and tell you how it goes before the first act is over. I still watch shows of course because its not the surprise i am after, its not something different, its something i haven't seen. You go on a journey and find out which twists and turns its going to take. You wait for the surprising moments of course but you also enjoy the obvious ones, like the hero winning in the end. You know how the heroes journey goes right? Its a literal roadmap for most stories. Does that mean its not fun to watch a heroes journey? Hell no. People love that shit.
Sometimes we get big things that revolutionize the way stories are written, like gay characters or any other taboo subject in storytelling and media. You couldn't do them without all sorts of restrictions so the first few times it was exciting because its new. Now however those things that used to be unheard of or undone are done and sometimes a lot. Within each story however is the potential for anything that has ever happened to happen. The fun part is seeing where it goes and enjoying the ride until you want to get off. The start of Arifueta or whatever was great! Now its become pretty much edgelord garbage. People still like it though, i just personally would have preferred a different direction. We all read for different variations of the same core reasons. Something being un-original does not stop it satisfying the desires of a persons inner workings.
Anyway this has become a bit of a ramble so ill stop here. Long story short "orginal" isn't really as simple or good as it may seem.