I remember people saying they hated the Datalog in XIII because it was required reading because it has crucial info for the story you will not know about unless you read it, while they would have liked something like that in XV just to have bios for the characters and recaps on the events that have transpired so far. I mean KH does that too, but the way XIII series handeled it is the way to not do one.
Like is the War of Transgression even mentioned once in the story for FF13 despite being a major event from the past? Etro isn't even mentioned once in the game either and even in XIII-2 and LR only gets fleshed out in the Datalogs instead of the game itself properly, same as whole fleshed out backstory for Caius, Yeul, Lindzei etc, that never happen during the games dialog or cutscenes.
The way the Beastiary works in XV as it is now is more like a Pokedex, and the character Bios in Comrades is basically just a brief description of the character and who they are, rather than page and pages or compulsory backstory that you can only find there. Even the Cosmogony passages in XV are found within the world in the books that you can find in different places, so them adding a menu section that collects all those to read the ones you found is basically the same thing as reading Xehanorts notes or like reading the documents you find in Ep Prompto/Ep Ignis.