macOS is still somewhat like this, if you avoid the "full screen" maximize just double clicking the titlebar will only grow the window to fit the content rather than have the window to fill the screen.

Its a lot like papers on a desk, and I know tons of folks here don't care for that model but I quite like it, especially in conjunction with stage manager.

I’m on macOS, it’s where I started working this way… uh… 12ish years ago.

Still using Spectacle for window management, despite its being long-discontinued. Still works, never a problem or glitch at all.