What I’m asking is if (and the answer is probably yes) UE4 supports a game world filled with players who are constantly changing the environment.
Best example could be like a minecraft server, just bigger scale (like destiny?)
thanks
I wouldn’t try making games of this scale as an amateur. Just a tip 
Brick Force is pretty close to this and was done with Unity 3 http://www.brick-force.com. So UE4 should be fine as well. However, Brick Force is not an MMO but just a multiplayer game.
A persistent MMO world usually requires so many changes to any engine that there isn’t much of a difference if you go with UE4 or any other engine or just start your own engine from scratch. The reason why an MMO may use an engine like UE is mostly because of the editing tools and prototyping, and to install an early workflow so that the art and design teams can already start in parallel to the coding process.
If you want to make some hobbyist MMO I would recommend to either go with an engine like the Hero Engine, which is specialized on this task (yet Star Wars: The Old Republic still claims they had to completely recode even this specialized MMO engine, but for hobbyists it should be fine), but there will be limits for turning it into something like Minecraft, or go with UE4 and just multiplayer maps instead of a full persistent MMO world.
However, in both cases I recommend to start VERY low. Developing these kind of games will take years - even for a team of highly trained professionals - so starting with an easy low end game and - this is important - finishing it(!), should always be the first step. If you plan ahead, you may even be able to reuse art assets later on.