On a local network, it's not significantly slower to run most apps through X11 forwarding than running them locally, and I use this extensively. The only daily application that's too slow is a browser, but Firefox (and before it, Mozilla did it too, and before it Netscape) automatically opens calls to the browser in the existing local window anyway (and there's always some pre-existing Firefox window open), even when running on some markedly different system (POSIX for the win).
When I used MacOS more regularly, Quartz always was the first application I installed.
When I see the comments from philistines unable to understand the obvious superiority of the one true Unix way, I always think of this Dilbert comic : https://dilbert.com/strip/1995-06-24
It was "slow" when I did it over 10Base2 Ethernet spanning an entire building. These days our CPUs are several orders of magnitude faster, and so are our networks. I don't need it to play the latest 3D games, I need it to display a user interface to an app that runs on a different machine. It's plenty fast enough.