I didn't really explain my objections very well in such a throwaway statement. My issue isn't that those things exist; pretty much the opposite. I think it's good that they exist and they almost certainly always should. My problem is when app A implements tabs differently from app B, app C uses the same shortcut for switching windows that app D uses for switching tabs, etc. It just all seems so disjointed.
What I want is for an OS that treats things like tabs as first-class citizens, not a byproduct that each app implements in its own way.
macOS actually has native tab support built in. It supports everything you’d expect from a tab system, including merging windows into tabs and splitting them back out. All third party devs have to do is opt in and tell the OS which windows are intended to participate. It’s been a feature for a long time now.
Problem is that most third party apps don’t opt in and instead reimplement tabs themselves. It’s mostly native Mac apps made by small boutique developers that use native tabs.
I only very recently changed my System Settings > Desktop & Dock > Windows > Prefer tabs when opening documents to "Always". I'm pretty sure the default is "In Full Screen".
Now, something like TextEdit creates new files in new tabs rather than new windows. It's great! But by default, everything on macOS seems to use windows rather than tabs. I don't even think most people know about the "Prefer tabs" option at all.
What I want is for an OS that treats things like tabs as first-class citizens, not a byproduct that each app implements in its own way.