No, the Apple adapter works reliably but is priced high. Many third-party alternatives in the $5 range work just fine.
You have two main types: an actual hard adapter or a flex-cable dongle. For heavier flash drives, I highly recommend the flex cable to avoid putting excessive strain on the USB port (I would also recommend shying away from any hubs that are physically attached to the side of the MBP.) Both the hard adapter and flex cable would work fine to connect your iPhone to the MBP.
Alternatively, you can also purchase new cables that go directly from USB-C to the connector you need (such as USB-C-->Micro B, USB-C-->Lightning, USB-C-->USB-B, etc.)
I just replaced all of my USB cables with USB-C to the appropriate type of connection (micro-USB, etc) cables, no dongles, same number of cables, same amount of space needed and the cost wasn't much more than the dongle.