What's ridiculous is condemning something based on your own ignorance. The keyboard shortcut is Cmd-Backtick ("Cycle Through Windows") and it works in all macOS applications.
There's simply a more sharply defined distinction between applications and windows. Cmd-Tab is for application switching.
you happen to be talking to someone graduated in UX design. and from my high horse I often don't fall for personal taste when writing UI critic :)
if the user wants to move to a terminal window they have open in the background, which key combination do they press? alt+tab or alt+backtick? they have to stop and actively think about which current window is highlighted. is it the browser? or another terminal? this completely kills the action fluency of a keyboard shortcut.
This is generally a non-issue, but even if you are getting tripped up consistently, the OS literally tells you at all times what application currently has focus
People have already given you the answer, but macOS also supports tabs in nearly all the stock apps, so CMD+{1,2,...} is an even nicer way to work with multiple terminal windows, if you're not a fan of tmux. I don't think any stock Windows applications allow tabs.
