Fair call, that.
I don't believe there is a constant need to be original to be relevant, but you do need to be consistent, palatable (at least in some shape or form), and have a concept that has the basic ability to generate interest from a fundamental level. Obviousness achieves all of those things, so to combat obviousness taking over, you need to simply attack the idea from a different angle. An angle that has personal value to you as the artist, and an angle that can be relatable to the viewer.
Damn, I feel like a philosopher!!