do you think SE will be able to do that at some point? And then autogenerate the terrain based on the known info about the planet?
I could imagine the program doing that in the future, but not in the next few releases. Such a feature would make Steam the ideal platform for SE, however, since instead of manually downloading and installing the update packets or patches from the game site, Steam would automatically update your game for you each time you launch it with an internet connection.
he quality of the terrain on ExoExplorer isn't on the same level as SE though is it?
As I said, it is broadly similar to early SE graphics (this is from version 0.8.5.0):

I think we've been pretty spoiled by
SpaceEngineer lately with the graphic developments in the latest releases of SE. I'm sure if I had discovered exoExplorer before I found SE, I would have considered it quite amazing.
And you cant explore the terrain in 3D using a simulator the same way you can with SE?
Yes you can, but it isn't as glamorous as SE.