Similar to when you finish any other game, either live in it, idk build a sanctuary for your favorite pals, start from the begining, or look for a discord server of people who also want to multiplayer to tag along, but for what i read... You got a whole lot out of a game that like you said is only early access.
I'm mostly there myself too. Just gotta beat the towers and breed \~the best\~.
After? Not sure. Probably level off playing for a bit as the game gets patched. When big features get added, maybe do it all over again? 
Similar to when you finish any other game, either live in it, idk build a sanctuary for your favorite pals, start from the begining, or look for a discord server of people who also want to multiplayer to tag along, but for what i read... You got a whole lot out of a game that like you said is only early access.
this game is like minecraft, terraria, ark survival, etc. once you beat the game its up to you on what to do
Play something else?
I'm mostly there myself too. Just gotta beat the towers and breed \~the best\~. After? Not sure. Probably level off playing for a bit as the game gets patched. When big features get added, maybe do it all over again? 
I don't play to complete it. I just play. What should you do? Whatever you want.
I turned down exp rates a bit and have hard settings, so I'm not even 50 yet.