The biggest issue was some of the missing reflection APIs. With netstandard 2, it's no longer a problem. Also, Bogus, for some reason when tied to netstandard 1.x didn't work on Xamarin. But now, with netstandard 2, it works on Xamarin.
@gregsdennis I've been working on trying to remove Newtonsoft as a dependency to remove issues like that. IIRC, issue #89 is the same kind of issue. Eliminating Newtonsoft completely is still a work in progress.