I just think it goes to show how little the window management of desktop OSes has improved over the years that desktop applications have had to up the ante...

I also think the differing behaviour between different apps implementing split panes (e.g. keyboard controls for creating/switching) is very annoying. Somtimes this flies in the face of any desktop's native window splitting or tab support as e.g. an app stops supporting multiple windows. For example, current browsers don't have a good way to configure usage without tabs, and at some point removed support for setting the window icon to the site's favicon.

Perhaps. Maybe iTerm's recent browser plugin, though useful, is a symptom of that lack of desktop UI progress.

Labeling a legitimate question as “negative” while not really answering it is unproductive.

Um, what makes this "just asking questions"-style dig "legitimate," while my point that nobody ever asks that about any other software is dismissed as "unproductive"? If anything, slapping labels on things without giving any reason at all is what's unproductive.