What Was Actually Going On in Pirates of the Caribbean

Have you ever wondered why some VFX in older movies, like for example this shot in Pirates of the Caribbean 3 , look far better than the ones in newer, more modern movies, like this one in Black Panther? Even despite the technology being a lot more advanced nowadays, we still often see big Hollywood movies with crummy looking CGI that almost seems as though it's been stuck on with old duct tape as an after thought.