Complex sentence: And not only is there a shift in what backpackers carry, there is also a change in what they use to carry that gear: backpacking is becoming less and less reliant on the physical backpack in its initial form.
Split into simpler sentences: And not only is there a shift in what backpackers carry, there is also a change in what they use to carry that gear. Backpacking is becoming less and less reliant on the physical backpack in its initial form.