Scottie is really smart, he picks out anything that's non-kibble (i.e. if there were chicken or cheese bits, he'd be able to pick it out crumble by crumble).
If you want to keep trying with the kibble, try soaking the kibble in bone broth. This link has a video and a blurb on how to make it and the benefits of bone broths for dogs (old, young, or sick):
Bone Broth Is Excellent Nourishment for Older Pets I personally would avoid canned broths as there is a lot of sodium in it.
It's good for them and the bone/meat flavour infuses the kibble and I think dogs really like it. It's good for hydration too. Very nutritious.