I definitely agree with @MoiraNotRuby.
We have tried to find the middle ground. So when my DD wanted Instagram at 11, we said yes, but the account was also set onto my phone, so DD knew I could see everything she did. At that age, she was pretty innocent but I still had to talk to her a few times about her tone, and how she came across in text etc. Also had to chat with her about chain messages that went round. As she became more mature, I was able to take a step back, and now her account is no longer on my phone, although both DDs know that whilst I'm paying their phone bills, I know their passwords and have the right to check if there's ever anything untoward. It used to be the younger daughter snitching on her big sister, but these days my eldest (17) will sometimes tell me about things my youngest has done.
The thing I noticed is that my eldest has friends who weren't allowed SM, so they just set up their accounts on friends phones and would log onto Instagram onto their friends phones, so their mums never knew they were doing it.
My youngest has a friend who wasn't allowed a phone at all until she was 13, and is not allowed any SM. I think she gets left out a lot. Friends are chatting every evening via snap etc, but this one friend doesn't get to take part in anything as she's not allowed on it. It has also meant that she's left out of events. They organise via SM what / where / when they're doing things and once decided they'll send a text to the non SM friend to invite, but if she then can't make it, it's kind of tough. So she does get left out a bit which is a shame.
And yes, Snapchat is in fashion, TikTok is too, but my DC don't like that. They think the dance thing is silly and Instagram is not really used at all anymore.