Complex sentence: She continued to publish sporadically after 1913, but her work lacked the brilliance of her earlier years and depended upon the retrieval of decades-old artwork and concepts rather than artistic growth and expansion.
Split into simpler sentences: She continued to publish sporadically after 1913, but her work lacked the brilliance of her earlier years. What success she enjoyed with her later productions can be attributed to the retrieval of artwork and concepts from her past rather than artistic growth and expansion.