I recently installed Ubuntu on my old MacBook Pro 2016 (
ubuntu-22.04.3-live-server-amd64.iso). Why does the UI look like a terminal (see the following picture) rather than all the pretty UIs that I see from others?
The ISO you used is the Server ISO. It's designed to run on a headless machine without a GUI. You need to use the Desktop edition installer, not the server edition installer.
While theoretically you can get the desktop up by running
sudo apt install ubuntu-desktop, if you haven't done anything with the machine yet then the simpler solution is to download the Desktop ISO, make an installer disk for it, and then install the Desktop edition and wipe the Server edition from your system. That's one of the easiest solutions.