The social media that exist today do so because of pretty extreme evolutionary pressure in competition with many other similar and dissimilar platforms.

The core premise formula of these corpo social medias is often not actually bad in a vacuum.

If you think about legacy social media:

Facebook is about sharing and following microblogs from your friends and acquaintances and staying in touch. YouTube is about sharing videos. Tumblr is about niche interest full-fat blogs. Reddit is about making it easy to create a forums.

MySpace is for uhm uhh something like Facebook and Tumblr mixed together, which just doesn't hold the appeal because those crowds are almost completely separate. IMO it actually works well, but VK (back in the day) did it better IYKYK.

Then your second gen ones:

Instagram is about sharing photos. Twitter is for news commentary and opinion microblogs. Google+ is uhhh like Facebook, Twitter and Instagram in one.

Ofc you also have Vine which just failed to monetize but was actually a good concept that people loved.

Then you have your third gen ones like:

Snapchat is like Instagram but for messages. TikTok is like YouTube but short and for phones.

YikYak is like Facebook but uhhh.

You can even trace it back to wacky dot-com bubble ideas with some sort of funnyshoesfordogs.com that has a gimmick but no longevity and then the more refined but rough sites of the mid-aughts competing with each other for new users and for early adopters against the then dominant petty dictatorships of various forums.

So copying existing platforms is not a bad idea to start with. Perhaps out of this we can see a new demand and meet it with a federated structure to get ahead of the corpos as well.