Is religion in Westeros oversimplified? I mean there are no religious wars, most of the nobility are irreligious or openly disdainful of it, inter-faith marriages are not a problem, there is practically no religious syncretism or schisms anywhere, people worship the Old Gods and the New openly, and the Faith seems by and large toothless.

Oversimplified? Yeah, somewhat. 

But I do want to push back a little bit: we have evidence of previous religious wars, from the Revolt of the Faithful to the Andal Invasion to the Blackwood Rebellion against the Teagues. And arguably the idea of the “Old Gods and the New” is a form of syncretism. 

And in the wake of the Sparrow Movement, can we really call them toothless?