How can I write extensively on a shallow topic/ object? A topic which doesn't have a lot of content or substance.

Answer 1

Depending on the topic, you could add in your own personal information or experiences about the topic

Answer 2

What are you writing for? If it's fiction, you can personify the object by turning it into a character. If it's scientific, you can research its history. If it's a shallow topic, find out how people perceive it.