Can't connect to localhost after switching to WICD

I'm using Ubuntu 20.04 and, due to my Wifi often cutting out, I decided to disabled network manager and install WICD instead (using this tutorial).

It works great, and my Wifi doesn't cut out anymore. Only problem is that I can no longer connect to localhost. Can somebody please help me?

$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d