The reason the lore tech issues aren't fixed yet.

Looking over some recent talks riot has given I've found a possible decent reason why the shurima/shadow isles lore pages aren't complete yet. The problem is exactly what we've been questioning "why would pages of text be so hard to implement?" and thats the answer, the new lore pages that will to be coming will include audio recordings and video along with the character pieces.

From an interview Tom Abernathy gave before leaving riot

Basically, what we're doing is: Any storytelling medium that you can think of, we're either exploring the idea of doing something in it, or we're actually already kind of doing something in it in-house — occasionally working with outside folks. And that, for us, for the time being, that's gonna be the way it has to be. Our particularly rich storytelling stuff, most of that will probably happen outside the game experience. But, that said, we can explore a lot more channels than we have.

Like what I said with the bios. I mean, the bios in the future could be.... first person, they could be second person, they could be third person. They could be future, past, or present tense. They could be poems, they could be songs, they could be audio files, they could be videos — like the Jinx video. They could be anything we want them to be— Well, anything that we can get the guys who make the client make work. Or, if not, we'll have them live on the web, or something. Source

This approach requires riot to implement solutions for audio and visual packages and i think explains why Riot's website team is taking a bit longer to implement the lore pages.