Every phone of Samsung is loaded with interface apperances that match the physical body in the best way. The preloaded widget looks best with the device you've purchased.
Ofcourse third party widgets can replicate the S8 clock widget.
Thank you for sharing your concern. We would like to inform you that as of now there is no official way to get update S8 concept in your A5 (2016). Please stay tuned with community for further updates.
