The ability for the software to do so is there in regards to multiplayer capability, with certain limitations regarding peer to peer design versus dedicated server design, which can be overcome with third party tools and plugins.
The bigger factor is the author's ability to see the project through.
As for your specific examples such as Minecraft and Terraria, which are chunk based infinite or otherwise large scale designs with active/inactive areas - C3 does not particularly have any tools to help you manage those types of systems, making it significantly more difficult to create than others.
Regarding "something online", yeah that's well within the reasonable scope.