I, for example, brought this book.
In a blink, I found myself in an unknown land, greeted …
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It's not a very good book, in my opinion, it's either a satire, parody, or most likely rip-off of one.
I think I know the book it tries to copy...
This one is the isekai (check).
It has a system, thus it is a LitRPG (check)
There are no levels, though. There are ranks, ranks aren't chronological, number-based, but more of the really vague titles taken from xianxia cultivation novels which the novels tried to make fun of. Still, there aren't levels, and progress isn't chronological. It jumps around without any rhyme or reason, and usually appears out of nowhere. (not-check)
However, despite this is xianxia novel, there aren't cultivators, there are mages (which are all a-holes like cultivators are), setting is weirdly western, most if not all names are English (save one or two). There are creatures which are unlikely in xianxia too.
There are dungeons. Even ranked dungeons. (so check)
But no one runs those dungeons. Only person who ever visits them is the protagonist, and his tagalongs, and does it despite the fact he is a contrarian who is explicitly against doing the game stuff, dungeon diving, and adventuring... (not check)
There aren't any adventurers. They are referenced, usually by the MC, and he usually badmouths them, despite never encountering any adventurer per se.
There aren't any adventurer guilds either.
There are, of course, sects, like in xianxia, and there are magical academies, since the story cannot decide which one is which...
But none of them are interested in the dungeon diving.
So, it doesn't seem that all stories follow the same patterns. In fact, this story barely has any plot at all, and most of the book revolves around the protagonist breaking the 4th wall talking to the audience about how avoiding any plot is smart.