I was told gum stimulation & growth is the only option for the space between my crown and neighboring tooth. Is it true? (Photo)

See dot on photo, this is the place where food gets stuck. I waited too long to have my root canal and crown(I noticed decay over year ago). My tooth feels like it did 6 months ago. Looking for a second opinion. They filed the sharp edge problem solved. New issue-gap between 16 -15. Food gets caught. Gap underneath teeth (not at gumline). dentist told me I need to stimulate my gums. Does not make sense to me since the food enters at the bottom of the teeth. feels like a gap or sloping hole.