Simplicity is …
Simplicity is the ultimate sophistication (Leonardo da Vinci).
In my opinion, there is always, or at least should be, a place for simplicity in research and instruction.
The research that is simple is accessible to our colleagues (researchers) and to other people. By making our research simple, we allow it to have a bigger impact: researchers can continue our line of research while other people can put our research to practical use (e.g. to adopt more effective methods of learning languages, to communicate more effectively in their own culture and interculturally, etc.).
The instruction that is simple helps learners to make more sense out of what they are learning. It also makes the learning process much more agreeable for both learners and instructor.
Therefore, adding simplicity to (not oversimplifying) our research and instruction is beneficial as it is, probably, in any activity including creative work.