The GPU in the brand new Mac Pro is identical feature-wise to the GPU in the almost 2 year old iPhone 13 mini (both are metal Apple8 family).
I guess there are some features related to the architecture itself like memoryless targets and tile memory, but on the whole these are GPUs that are playing catchup (and are doing it very very slowly) and don't have any of the exciting new features available on current-gen windows dGPU.
You could be correct that dGPUs will eventually go the way of the dinosaur, but that's a problem for the future.
The newest GPUs supported by intel MacOS are RDNA2 based, from late 2020, so age of cores isn’t the win you seem to think it is.
And yeah, the pure “gpu” part of the “gpu” on the SoC isn’t amazing, I’d rather have RDNA 3 or Ada cores using that die space budget than apple’s cores. But things like the media engines and other specialized accelerators make an Apple SoC better at many specific tasks than even a generalized GPU with 10x the power budget. The fact that the gpu of an M1 or M2 ultra can access 100GB+ of RAM at 800GB/s without a cpu or PCIe bottleneck is something no other GPU can do.
And that’s part of why dGPUs are dead men walking — duplicating RAM in two places, plus adding system bottlenecks and overhead is not a winning strategy now that on package RAM and huge SoC dies are possible. If AMD built a consumer SoC using zen 4 and RDNA 3 using the number of transistors and die size of an M2 ultra, it would demolish their 7950x plus 7900xtx CPU plus GPU, as the m series chip has more transistors than those two combined as well as the massive improvements that lack of overhead and unified memory bring. The future is SoCs, it can’t be avoided. You could have 24+ cores of zen 4, plus at least the entirety of a 7900xtx plus all the extra accelerators apple uses, plus huge cache, plus 800+ GB/second access to 100+ GB of shared RAM. And they wouldn’t be designed to sip power like apple’s designs, AMD would tune that mother to put out a combined 500 watts with some sort of monster cooler. It’d be expensive as hell, but it’d make building your own PC from off the shelf parts feel like hooking up a horse and buggy for the Indy 500.
It’s lame for us tinkerers and upgraders, but the future is SoCs. There was a time you could build a whole state of the art computer with an article from a a magazine and access to radioshack. Then we needed a few specialized components only PC makers supplied, now building a computer has evolved into attaching about 6 proprietary, highly complex parts to a case and power supply, and soon even the RAM, CPU and GPU will merge into one part. But hey, you can still pick your cooler, “motherboard” case and powersupply!