Getting the 600 writers points, pulling the number from memory -- I could be off, is just one of the options. You don't have to pick it. See it as an indicator as to where you will eventually build a Writer's guild. A famous writer is born, known among the land, and later a writers guild is formed in their honor. Even if you want to have all your guilds in your capital there is still room for two more. So it's not really an issue is it? Or shouldn't be.
The mysterious stranger event, or whatever it's called, that gives you artist, merchant, science or engineering points is in that regard then similar. No need for an artist guild in the city. But it's an indicator on where you might want to build one eventually, if you pick that option -- I somehow almost never do. Not sure what buildings would be required for the other options, but something with the appropriate slot I gather otherwise they would then be disabled? Nah. Works fine like it is.