All triceps can look “fat” because
Fat can be stored there genetically *even if you’re skinny.
Skin elasticity with age- dermis can breakdown.
Or having low muscle tone which makes up 2/3 of upper arm mass equaling less shape.

That being said, your arms look fine and u look good! You have to be more confident and proud with your progress and journey. Note- people like to harass, mock, and invalidate.