Everyone on your list has taken a meaningful step already. They bought something, enquired, downloaded, booked or deliberately typed their address into a box. None of that is passive.
That is the whole advantage. Paid social starts from indifference and pays to overcome it. Email starts from a decision the person has already made. You are not interrupting a cold feed, you are following up on interest that exists.
It is also why the same message performs so differently across channels. A product email to warm subscribers and the same product as an ad to a lookalike audience are not the same job, and it is unreasonable to expect them to convert at the same rate.