The minds that were behind LiveJournal, Friendster, and MySpace, to name just 3 other social platforms that had monthly active usership in the millions, were not as disgustingly criminal and unethical in nature as the mind of Zuckerberg, so, to answer your question, another online social platform could be more civil and nicer, and not as aggressive (with auto-playing, auto-looped videos, for one thing), and manipulative, and silo-creating in terms of the design and algorithms in the same way, and could be far less ruthlessly greedy, invasive, and devious toward its users in terms of the requiring, gathering, selling, and sharing of those users' data.

An online social networking platform could even take a total different format than one that invites users to upload all their real personal life information and photos; there could be a platform as one where the users are playing ficitonalized characters in a make-believe world, and there isn't the same severe data-mining and harvesting of users' minds and lives, let alone with clear algorithmic and editorial favoring of political-themed content; I'm thinking first of something like the The Sims from 2000 to 2015[0], but there is a now a certain game that has become the de-facto social network of pre-teens to early teens, and that is Fortnite Battle Royale - see these 2 articles from December 2018[1]-[5]. Yes, there are other risks and dangers with such a platform (where gamification is taken to a much further extent: you're playing much more of a character in a game than you are with the "character" you "play"--in the sense of "portray" and "direct" on Facebook)[6], but it's not, in my view, nearly as immoral and irresponsible as what Facebook does.

[0] Sims popularity, as recently as 2014, when the latest version of it was still the #1 computer game:

https://simscommunity.info/wp-content/uploads/2015/05/Screen...

[1] Charged: Fortnite isn't a game, it's a place - As social media becomes ever more toxic, Fortnite has become the new social network and a place to hang out where you go to talk to friends

https://char.gd/blog/2018/fortnite-is-the-new-hangout-spot

[2] WSJ: How Fortnite Triggered an Unwinnable War Between Parents and Their Boys

http://www.wsj.com/articles/how-fortnite-triggered-an-unwinn...

[3] See the selected tweets here, including: "Fortnite is the tween generation's Facebook (at least for boys). Spent a few hours last weekend with a friend's 12 YO, Fortnite is the platform for his entire social/academic life. FYI i was labeled an 'old noobie'."

https://www.techmeme.com/181222/p8#a181222p8

[4] The astonishing usership stats (scroll down to the list):

http://www.businessofapps.com/data/fortnite-statistics/

[5] Many more stats:

https://en.wikipedia.org/wiki/Fortnite_Battle_Royale#Player_...

[6] Impact:

https://en.wikipedia.org/wiki/Fortnite_Battle_Royale#Impact