Can be iPhone used to burn CD/DVD?
The Apple Lightning to USB adapter is not powered, so the trivial answer is no. As you've already realized, many powered pass through USB devices exist and some surely have enough power For most USB bus powered devices - even a motor and optical drive.

The slightly more complicated answer is also no. The software interface and software drivers to recognize a burnable media device isn't programmed into iOS (or iPadOS).

All your good work connecting the device will be for naught without software changes. I bet someone with a jail broken phone and skills could cobble together open source drivers and attempt to load them, so I'm not saying that this isn't theoretically possible, just that it's not plug and play due to software issues and potential power issues.