As the father of two Gen Z kids I can confidently say they couldn't give two shits about FB or the Gram. They have zero interest in X. They kinda like YT. They much prefer Snap and TikTok. The only FB they use is work related (meta has a platform for that) and as marketplace when they sell stuff.
I have a LinkedIn I never filled out. I do have a reddit but I very rarely use it, most of the time I do, I use browser and don't log in. I'm currently working towards unwinding myself from Google. Then I'm done.