Zane Grey’s writing is corny, clunky, and amateurish.
“Out of date” is a polite way to describe his language and attitudes, which are casually racist. His characters, at best barely better than cartoonish, adhere to age-old sexist stereotypes.
The historic popularity of Zane Grey’s work can only be understood as his readers’ recognition of their own values in the “Old West” mythology of white settlers, ranchers, rustlers, and gunmen as the heroes of a white-supremacist melodrama. (Or else, if you came to Grey’s stories in your youth, you might have a nostalgic love of them.)
The anti-Mormon screed in Riders of the Purple Sage, too, would have appealed to most of his original readers.
Louis L’Amour adopted Grey’s basic ideas, created a formula, and cranked out a prodigious number of stories built on it.
The Old West in the novels of Grey and L’Amour is a largely lawless Hobbesian state of nature in which evil men seek to rule and dominate by any means necessary, while good men band together under the leadership of a hero to defeat the villains and protect their land, property, and families. These novels are quintessential boys’ fiction, allowing male readers to wonder if they would be wise, brave, and strong enough to defeat the bad guys.
Tony Hillerman’s detective novels, set in the same region a century later and featuring Navaho policemen Joe Leaphorn and Jim Chee, are much better on all counts. Within the conventions of the genre (we still have melodramatically evil villains) Hillerman introduces realistic, well-rounded characters, authentic portrayals of indigenous people and their cultures, and female characters who are something more than patriarchal caricatures. If you enjoy detective fiction, I warmly recommend Dance Hall of the Dead as a good introduction to Hillerman’s work.