Not necessarily. A larger sensor does require a lens that covers a larger image circle, but that does not automatically make the lens more complex. In fact, larger-format lenses are often easier to design for high image quality than smaller-format lenses.

Historically, medium-format systems like Hasselblad used optical formulas similar to 35mm lenses, just scaled for the bigger format. Larger-format lenses are still precision products and can be expensive, but they often use simpler designs with fewer elements than highly corrected 35mm lenses.

One reason is that small-format SLR lenses—especially wide angles—face tougher design constraints because they must work around mirror-box and flange-distance limitations. Medium-format systems can avoid some of those compromises.

So the key point is: a bigger sensor means bigger lenses and a larger coverage requirement, but not necessarily “incredibly complex” lenses. Sharp, well-corrected medium-format lenses are demanding to manufacture, yet larger formats are often optically more forgiving than smaller formats at equivalent angles of view.