If I remember, Writing obsoletes Elder Council, and a couple other buildings that give +

or +

%. It's partly alleviated by opening up Written Tradition civic. It's a fairly common problem in the game where buildings obsolete at the tech which gives you their replacements, so you lose out on the bonuses until you 'rebuild' the newer buildings.
The devs are working on tweaking all the buildings and techs constantly, and I think the oral -> written science drop is on their radar.
I think a good idea for the Myth buildings would be when you discover Writing they obsolete, but you get a free 'National Mythology' building(s) in your capital that gives you a small +

and a large +

, and you could modify these values up and down with future techs like they do with the University. I think you can use obsoleted buildings as building prereqs, so you could have multiple National Mythology buildings:
National Mythology (Predators) - Requires Myth of Cheetah or Bear or Lion or etc.
National Mythology (Grazers) - Requires Myth of Bull or Deer or Horse or etc.
These would also give poor hunting civs a bit of a leg up because they might be able to get most of the broad categories even if they only had 5 or 6 myths.