Depends on the direction
If going in a slice of life direction - steal a lot of stock sitcom plots and use those. Add actual stakes, drama. Think every '80s high school movie ever. Karate Kid, Cobra Kai, etc...
If going in an action-adventure direction, focus on worldbuilding and give us a lot more of it. Really flesh it out. Maybe focus specifically on French mythology and mysticism instead of this cliche 'vaguely ancient Tibet monk' plot. The whole ancient monastery plot reminds me of old '60s comics like Batman or Doctor Strange and so on. It almost smacks of cultural appropriation but I don't want to have that conversation. I understand the show has Japanese and Korean creators so maybe you could draw from those influences as well but because it takes place in Paris, it should primarily a French show. Show me the thousand years of French culture. Really lean into the influence of a French, Japanese, or Korean background when writing the show.
Of course, don't flesh it out to the point you leave absolutely nothing to the imagination.
A lot of things just need to be fleshed out in general, given we're already 4 seasons in and know very little about the setting or the characters.
I think the worldbuilding needs to be a lot more solid to allow the characters more chance to shine. That being said, it's like the creator is making the world wider and wider. More characters, more locations, more macguffins. A world with the width of an ocean and the depth of a puddle. There's already a lot to explore here. We need more depth; we need to explore what we already have.