So, there is an issue with create which could be because of three things: it's not playing nice with other mods (I imagine there's probably some incompatibilities with rubidium if they haven't been resolved), some dependent of create is causing things to crash (createchunkloading for example), or the version of Forge is too new and some change broke create.
It's difficult to determine which this is, so you'll need to experiment.
You're making a PlacementModifier correct? Regardless of what you choose to do with the feature, it will attempt to generate for every chunk. The placement modifier determines which block positions to apply your feature at within the chunk. So, if you return an empty stream, your feature won't be applied in the chunk. If you return a stream of one or more positions, it will attempt to apply the feature at those positions.