Adobe has access to plenty of APIs on Windows, yet it didn’t run any better and was an incessant security nightmare. Why would anyone have a reason to believe that Adobe would’ve done a better job on the mac than much flexible windows?
Adobe’s current performance on Windows and Mac in 2020 does not add any backing to that argument either.
Flash ran massively better on Windows than on Macs. One of Job's specific complaints was that it didn't run as well on Mac as it did on Windows. And that's because they couldn't get the same graphics hardware access they could get on Windows.
The flash player was a perfectly performany piece of software. The piece of shit programs people wrote for it were slow but that was not inherent of Flash. The same people went on to wrote piece of shit HTML 5 apps that peg out your fan just as much.
Adobe’s current performance on Windows and Mac in 2020 does not add any backing to that argument either.