I was sitting right next to the router about 2-3 feet away, so it definitely isn't distance or obstructions.
So separate 2.4 ghz and 5 GHz ssids. Connect your device to the 5 GHz ssid.
On the router, set the 5 GHz channel as 80 MHz in an unoccupied channel. You can find what's up in your local area using an app like Ubiquiti Wifiman on the app store.
This should get you 400-600 mbps on your 3x3 AC capable MacBook.