Social media can be great, but as I’ve said on here many times, it’s not yours. Using social media to grow your audience can be a very beneficial thing, but moving your audience from that public network to a private channel (such as an email list) is essential to your long-term growth.
We saw this a few months ago after Donald Trump was kicked off Twitter (and lost that public audience), but he had done a very poor job of moving those users to a private channel and couldn’t sustain his personal website for even a month.
David Perell did a great job of explaining this in a recent short (6 min) podcast of his titled The Public to Private Bridge. Building that bridge to bring users across to your private channels isn’t something that you can ignore forever, and is largely the idea behind a marketing funnel — use your popular public channels to drive awareness, but slowly guide interested users onto your email list and other private channels for sustained growth.
At some point in the future, Facebook will become irrelevant, Twitter will fade away, and new channels will likely grow to take their place. Using those new channels will likely be a wise move, but working to move your followers to private channels is your best bet in the long run.