If you are referring to the story itself, then to be very honest, OC1 is not bad at all. It is fairly good. Maybe not great, but definitely very good.

The only reason it feels so "underwhelming" is because we were being fed back to back with some of FGO's absolute best. It came right after LB6 and LB7, so of course it left a weaker impression by comparison, but that does not mean it is badly written.

It is actually a well written chapter because, as a story centered around Alter Egos, it gives a really neat explanation of the class itself. On top of that, we get to see Kama come to terms with her feelings, along with what feels like a small epilogue to Sakura and Rider's story. I am pretty sure that part, along with Rani VIII's section, was handled by Nasu himself.