The flip side of point 3, and probably the better way to go about things in most cases, is to accept the fact that other people have autonomy and just let them do whatever the hell they're gonna do in most cases. If you have family members who eat too much or smoke or gamble or drink a lot, it would be ridiculous to cut them out of your life over it. Just get over the fact that they're not running their lives in the perfect, ideal way that you would and love them anyway. But if someone is in one of the the deepest, darkest pits of fucked-upedness that you've seen in your entire life, well....
Point 1 is stated a bit too strongly, which I tried to temper a bit by jokingly contradicting it. I think a lot of interpersonal stuff is best handled with Postel's Law: be conservative with what you emit and liberal with what you accept. There is a time and a place to offer advice to people, just as there is a time and a place to offer rebuke, shame, or a punch to the face, but these are terrible default modes of interaction, and I think apo likely shares my personal flaw of defaulting to advice far too often.
By all means, especially if you're dealing with someone in a deep, dark pit of fucked-upedness and you seriously want to help guide them to salvation, give them advice. But do so very deliberately. The stereotypical example of this is an "intervention", and I'm not sure how effective that particular modality is, but the basic idea of treating it as a very serious move that must be done as carefully as possible, with plenty of forethought and love and good faith, seems like the right approach. And if they never make a good faith attempt to change things in response to that, well...at that point, it circles back to point 3, and if you follow through on point 3, you're definitely not enabling them anymore. Although even then, there's still a chance they'll break into the house and steal the TV.