Yes, Sanders main problem as a candidate is he is very hyper focused on one issue (inequality) and very weak on others. He can talk all day about economic issues focusing on his key demographic target, but in terms of national security or foreign policy he has nothing particular interesting to say beyond a few boilerplate liberal sentiments. There's nothing inherently wrong about running on a dovish platform, but Sanders doesn't seem that interested in substantiating his foreign policy at all, which is dumb, as foreign policy is the area POTUS has most power over.
Bernie isn't a dove. He said we should destroy ISIS.
And looked so awkward saying it too. I think he's saying it just to say it rather than really believing it.