Personally,, I feel that their needs to be balance. We need to worry about ourselves and make sure we are doing what we should but at the same time we should care about other people to the extent we share to them what we learn not for the point of judging them but for the point of them having power, "knwoeldge is power."
It's because Islam is not an individualistic religion, we live in communities.
And the companions said, "we never considerd a person leaving an action to be kufr except salah." But how much salah does a person leave? maybe they pray once in a while or at home...that's why a person who doesn't pray, we shouldnt call the person kafir, that won't bring good, but we should teach them and be patient make dua for them. It's like somebody doing drugs, nobody will deny the person smokes but we wont just leave him to die, especially if he is a loved one or relative. Leaving salah is worse then smoking cuz it kills the soul:'(