Overall I'd guess it was a struggle to make Dr. Strange as formulated carry a film on his own. He needs a foil like Sherlock needs his John. Unfortunately, Martin Freeman already has another role in the MCU. To live on, Strange needs a partner to bring out the best in Cumberbatch, and a villain and supporting cast who are more than dire drones.
This review turned more negative than I had hoped. I don't want to scare you off of Dr. Strange. It's a solid entry in the MCU and a good couple of hours of entertainment but don't look for anything too special. It's mostly just a plot advancer for Infinity War.