How do I properly change the MAC address of my MacBook Pro?
Your command is correct, once you've prepared the network to be changed. Temporarily power down the WiFi before changing the address.
Doesn’t work on newer macbooks (2018 and later)
networksetup -setairportpower en0 off

Modify the mac address with the desired value:
sudo ifconfig en0 ether 88:63:11:11:11:11

Finally, turn on the WiFi
networksetup -setairportpower en0 on

I verified  with Catalina 10.15.4 and 10.15.5
uname -a
Darwin iMac.local 19.4.0 Darwin Kernel Version 19.4.0: Wed Mar  4 22:28:40 PST 2020; root:xnu-6153.101.6~15/RELEASE_X86_64 x86_64
sw_vers
ProductName:    Mac OS X
ProductVersion: 10.15.5
BuildVersion:   19F101