All of the scans were wrong. Nauvis isn't what we expected it to be. Vulcanus, Aquilo and Fulgora are all gone. There's Only Gleba.
Large total conversion mods.
Augmented or new ways of transporting materials - belts, inserters, pipes!
New ways to deal with enemies, be it attack or defense.
Changes to enemies or entirely new enemies to deal with.
Map generation and terrain modification.
New Ores and resources as well as machines.
Furnaces, assembling machines, production chains.