Facebook has huge overheads because most of their engineering time is spent on all the creepy privacy violating things they develop and the infrastructure to run them.
If we start from scratch without all that it would be possible to make a profitable social network for a couple of bucks per month per user (or a tiered system, so heavy users or “influencers” would pay more while the base tier remains free).
I'm not the parent, but from my pov FB is a net negative for society, so if they are unwilling to play by our laws, then I'd rather see them get the fuck out.
They won't of course, because it leaves the market open for grabs.
If they leave the EU though they don't need to follow European laws or pay European taxes, but that doesn't prevent European users from continuing to use the actual website.
Whichever European social network replaces them.
Facebook is a freak social network considering how long it has survived. People used to migrate every one to two years.