People are lazy. If you give people an easy way to "fill that void" they will do so, even if it's detrimental to their long term health.

No social media? People will still find ways to socialize. It might not be as easy, but they will do it. Maybe you'll even see a resurgence in social clubs.

I wouldn't say social media is just "filling a void". I feel like it's more accurate to say that social media is exploiting weaknesses in the human brain for profit and causing harm to individuals and society as a whole. I'd even say that it's preventing people from filling that void because it's sucking away people's time.

Imagine if a tobacco executive said "you remove cigarettes and people will just replace it with alcohol or other drugs or another vice altogether". It may be true for some people but overall we've reduced harm by fighting back against cigarettes