Okay, I think I have an idea of what's going on and why your dentist may be hesitant to replace this crown.
The gold showing through on the biting edge of the tooth is a sign of long-term wear, and the layers of porcelain that were covering the gold have been slowly worn away over time. This can be due to heavy biting forces, grinding your teeth at night, or a very abrasive material biting against this tooth (various other dental materials can be more abrasive than others and cause more wear over time).
Because this certain thickness of porcelain is now gone, it means that you've basically lost that amount of thickness in your bite as well. When the dentist removes this crown and goes to prepare what's left of the tooth for a new crown, it's likely that he will have to remove even more tooth structure to make up for that loss. When a tooth is already small to begin with, this removal of more tooth structure can leave very little tooth remaining to support a crown.
This does not mean that you can never have it replaced or get better cosmetics in this area. It just means it will be a little more complicated than simply replacing a crown.
If your dentist is not confident that he or she can do it well, you could ask for a referral to a specialist called a prosthodontist. They specialize in crowns and building up teeth where there is not enough room.
Does that answer your question?