Technically true, just as if you replace Meta with Amazon, Google Cloud, Etsy, eBay, the local city council, etc. If you don't have a diversified, multi-market, preferably international presence, you're not viable in the long term.

Of course, in the really long term, we're all dead. Meanwhile, the local mom & pop candy shops keep advertising and selling online and making ends meet.

What platforms have anywhere near the reach and services that Meta does for a marketplace/advertising?

I'm not personally a fan of most social media, but saying "they could go somewhere else" is a pretty naieve/ignorant response.