I'm very critical of Rihanna, as a fan, but not one of my criticisms is her needing to change her sound. The bitch always does something different. Hell from LOUD alone, we got West Indian and African sounds, reggae, country, Europop, country, and rap from the singles alone! She's very versatile. I honestly don't see the comparisons for WFL and OG either other than the fact that they are the same genre. On OG it sounds like she's "screaming" while on WFL she's rather mellow toned. The structure of the songs are very different.
So the b.s. that Rihanna doesn't try is null and void. She always TRIES different sounds. The only thing I wish she'd try is more songwriting, as I always say.