Relative to Psychtoolbox's longeviity, there are new ways of showing things on a computer, particularly APIs like WebGL and High Resolution Time for showing and timing things from a browser. On the desktop side, the variety of media libraries with python bindings has definitely grown during Psychtoolbox's adherence to Matlab.
Whatever the right approach is, I think the hard problem for Psychtoolbox is that a rather different kind of developer skillset will be required, both for the maintainers and the users. But that's not the fault of MacOS.
I happen to be conducting a brain imaging workshop today, and so far most of the hiccups have been caused by the quarantine rules in Catalina and up. Thankfully someone found a sudo command to fix it for a some of the participants, but I regretfully had to ask the rest to find a windows/linux machine to work on.