The usefulness of the visible light portion of the electromagnetic spectrum is subjective and depends on the specific needs and adaptations of the organisms in question. If complex life forms had never developed vision, the importance of visible light for those organisms would likely be diminished, as they would not have evolved sensory systems to detect or utilize that particular range of wavelengths.
Different portions of the electromagnetic spectrum, such as infrared or ultraviolet, could become more significant for non-visual organisms in the absence of vision. Many organisms, including some bacteria, plants, and insects, have adaptations to sense or utilize other parts of the electromagnetic spectrum. For example, certain organisms can detect infrared radiation for thermoregulation or ultraviolet radiation for navigation or signaling purposes.
It's important to note that the interaction between organisms and the electromagnetic spectrum is complex and multifaceted. The specific environmental conditions, ecological niches, and evolutionary pressures would shape the sensory abilities and adaptations of organisms, including their utilization of different regions of the electromagnetic spectrum.