> ...site has good readability...
Impossible. Because you cannot assume user's taste.
Also, if you think readability is not a taste, and you can make a mostly ideal configuration which can be applied to all the users, why don't you let the browser vendors to do that?
If browsers are shipped with ideal configuration by default, then now the only obstacle to prevent ideal readability is site-prodivded styling.
Actually Safari is trying to do this via Reader button, and shows always great result if it is available.
It's better for the user if a site has good readability without them having to do anything.