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Yesterday I spoke with my Apple Business sales rep again in the store and he said that After Effects and Premiere were running in some sort of almost like a virtual machine and were never really fully ported and written with native OSX programming, and that's why they are so sluggish and slow.
It isn't a "virtual machine" . It is probably more of abstraction target layer. Think of it more so as another layer on top of the operating system. Everything that is portable does this. The C programming language has a set of standard libraries for I/O , allocating memory , composing basic data structures. The POSIX (Unix) layer does the same thing. X Windows is abstraction layer on top of graphics. OpenGL is portable layer.
Qt is a library can use to write portable applications.
In a perfect world , applications can be design so there is a subset that this the user interface is completely decoupled from the part that does the work. The Mac native GUI would be attached to the "do the work" part on macOS and attached to a Windows GUI on Windows. Often either the underlying system libraries or the application abstractions are not that clean. Companies that port apps to multiple platforms tend to stick in a layer of varying scope and "thickness" to easy the porting problems.
One problem with Adobe's layer is probably for more likely that it is old. ( initially conceived to bridge OS X carbon (macOS 9) and Windows NT like gaps. ). It has probably had some major revisions ( to macOS Cocoa and somewhat newer Widows model ) but that may hurt about has much as help in different areas it covers.
Meanwhile Apple tends to ask for developers to "start over" every 10 years or so. Apple will cut off trailing edge systems off to free up resources to tackle the forward edge. Abode isn't so quick to cut folks off. Throwing in user base Windows makes that even more a priority. ( the minimal system requirements for After Effects are relatively recent Windows 10 implementations but Windows 10 has Win32 "get out of jail" cards for lots of apps to enable older Windows OS versions. Apple 'started over" with FCPX and are now repeating the benefits. Short term on the transition though, they took lots of "hate".
Second problem with Adobe's layer is that is probably has some bad choices baked in there. ( in that sense similar to Flash). Too much "job security" code (that nobody understands well so have to keep programmer X ) and it is not the "abstraction layer" that is the root cause problem. The problem is the choices in what to cover (versus what to have forked port teams cover) and how to do the abstraction layer.
That part is fixable over time if Adobe puts money and effort into fixing it.