We'll have to agree to disagree I think, and let things play out.
The Mac platform is hardly dying. I think we can all be accused of a bit of hyperbole on this subforum. Profits on the Mac lineup alone are equal to profits of entire companies.
The Mac's future is bright, so long as Apple delivers on its promise to release a new Mac Pro next year, updates its Mac mini, and releases updates/successors to the MacBook Air and iMac.
Those "cool technologies" are the future of computing, and will keep the Mac relevant and powerful for years to come.
With Nvidia, it's either you're all in or you're all out. There is no middle ground or compromise. I, for one, respect Apple's decision to steer clear from Nvidia and their foul play.
Sometimes you have to see the forest from the trees. While, yes, some extra gaming performance today is nice, it's not worth giving up Metal and having to submit to Nvidia's proprietary standards.
If you really want to game and use CUDA, then just buy a Windows PC/workstation and save yourself the heartache. Apple is locked into adopting AMD RTG graphics IP for the foreseeable future. We may even see that change someday to Intel graphics IP, especially since Raja Koduri (ex-Apple A-series graphics architect and ex-AMD RTG chief) and Jim Keller (ex-Apple A-series CPU architect and ex-AMD CPU lead engineer) are at the helm of Intel graphics now.
I'm sorry but with all the history behind the curtains between Apple, AMD, and Intel -- not to mention the giant cockup that was Nvidia's bumpgate -- I do not see Apple going back to Nvidia, ever.