I think cases like Haejin's are very few and I suppose there is no direct threat to Steem if only a very small number of users do it.
Abuse is the minority of the users, yes, but they are good to deal with now that we have the tools. Haejin and probably the @sweetsssj circle jerk (broken down by now though, now she's actually diversifying her votes) were probably the biggest extractors I know of.
I don't think that belonging to Steem means that we necessarily have to bring new users, I mean, it's the ideal and what we need to get ahead, but we can't force users to bring more users either (I'm deviating a bit from the subject).
I agree, we don't have to force new users. But the next Hard Fork will feature lite accounts. What this means is that new users can interact with a dapp, and the dapp creates them a wallet address when they sign up with email or other social media account (I think 3speak already uses this kind of method). They will be able to accumulate rewards right away and take custody of their account when they have enough Steem Power. This coupled with SMTs, and the ability to create a custom token reward system for an already existing community (like a Reddit subreddit, for example), means that people will be onboarded to Steem without them even knowing about it.