So you mentioned that
is a command that works for you, but you didn't mention whether or not you saw any output from your device. While I don't have a lot of experience with MediaTek processors, I'm aware that most of them share the same set of drivers and as a result, you should be able to download the appropriate "universal" USB drivers for Mac.
You won't be able to run
fastboot oem unlock
because your computer doesn't currently detect a device that's plugged in, even if your phone or tablet is displaying the bootloader screen and is connected to your computer over USB.
What I would recommend is Googling the name of your device and the words "USB drivers for Mac" in the same search query and installing the drivers from the manufacturer's website that comes up, or if downloads are provided by XDA or Reddit, from those sites as well.
From Googling, this link: https://forum.xda-developers.com/showthread.php?t=1917237 comes up that mentions that macOS doesn't require fastboot drivers, but I don't believe that is true anymore, although if that is the case and you cannot find drivers, I would redownload the Android SDK from Android Studio and use the latest version of fastboot from the platform-tools folder.