Semiconductor devices having interconnect structures with conductive elements configured to mitigate thermomechanical stresses, and associated systems and methods, are disclosed herein. In one embodiment, a semiconductor package includes a semiconductor die and a pillar structure coupled to the semiconductor die. The pillar structure can include a plurality of conductive elements made of a first conductive material having a first elastic modulus. The pillar structure can further include a continuous region of a second conductive material at least partially surrounding the plurality of conductive elements. The second conductive material can have a second elastic modulus less than the first elastic modulus.