Most of the big social media platforms these days try to find ways to identify you and know who you are, the best example of that would be Facebook, they force their users to use their full real name and if you don't then they will ban your account. Some platforms like twitter, instragram, tiktok, YouTube, etc. don't require you to use your real name but they can be just as harmful and most people on these sites upload pictures of themselves without any care about their own privacy online because giving your personal information has been normalized.
There are some new laws being passed in some countries and states that will require users to verify their age to use their computer or to have access to some social media platforms but as I specified above, this is just yet another way to get personal information about the user. Age verification is more than just entering a number, since you can't verify someone's age that way so the only way are to either send a picture of your ID or scan your face to determine your age. Age verification won't really protect the children online. I think the main problem is how lack of privacy online has been normalized. Children and adults as well should be taught to not share personal information on the internet and stay anonymous and to not give personal information to others, this used to be how it worked on the internet and the normal thing to do but after Facebook became a thing and people had to give their real name everything changed. There has been many case of people stalking Facebook profiles and finding where the victim lives or people scamming others or arrange a place to meet up as a trap.
Those platforms are addictive by design and are made to keep you on them as long as possible and trying to get your attention constantly. They have an algorithm that is designed to get your attention and recommend you content you are likely to interact with even if this content is upsetting or downright disgusting. So if you are someone who is suicidal you might get post showing up that encourage suicide or promote it even because that's what the algorithm thinks will get your attention. Those platforms are also very bad for people who have mental health issues and even for those who don't because it could easily lead them down that path. If you tend to react strongly to negative content, more negative content will get recommended.
Now not all of them are bad, but you can be sure all the major ones are. But there are good ones out there that usually don't collect your personal data, like mastodon, pleroma and many other platforms that use the activitypub protocol. The good thing about this is you can even host your own if you wish. For messaging there is IRC that is good. It's pretty minimal and usually doesn't even require an email address to use, but one may be required to register an account. Accounts on IRC are optional though, you could just choose a nickname and get in. There is also XMPP and Matrix that can be self hosted or you can join someone's server and those are usually safe as well and don't collect personal data. I would say those two are good alternative to Discord if you want a similar experience. Of course those platforms won't all be sunshine and rainbows, there are bad actors on any platforms and there are inappropriate posts on all platforms. You can't really avoid those, but at least you can avoid getting those recommended to you if you reacted to one of them. It's always good to limit your time spent on those in general but they are good alternatives.