It's not a place to show how good Software Engineer is by removing Title Bar and created something similar but hard to use. It's user experience & usage. (UI, UX). I could accept that someone still prefer to use LYNX, but not me.
Computer is made to help people.
The system (Gnome, Wayland, Mac, Window$) has its own Windows Manager system that people get used to it.
Now I have problem to use Opera because the Title Bar was gone. Opera becomes a rebellion in among the applications. Hard to use.
If Opera's developers wanted to show off programming skills, please have something that provides all compatible/synchronized functionalities as the Title Bar has (different system might have its own behaviour).