Of course we don't see the lead up in this case but there are many police shootings that could have been avoided by the officer maintaining space which also gives them time to make decisions. Just based on the video, it is likely that the dead guy would have engaged the cop no matter what he did but there are cases where the suspect wasn't agitated until the cop came up and started yelling.
With mental health calls especially, responding officers would be better to stay back and talk calmly unless there is an immediate threat to the public. It would probably make the interaction longer but if 'protect and serve' is actually the point, it would be worth it.