Philosophy s change over time. If that were the case, Luke would be no more a Jedi than Rey would be. He never really followed the Jedi code to a t, he did what he believed was right (he even uses dark side powers in rotj) As for snoke and kylo, I believe JJ confirmed kylo not to be sith. Nothing was confirmed or denied about Snoke. Even if he is not Sith, he follows similar ideal's from what has been shown about him and Snoke still hungers for power