The 2017 Ryzen 7 was very close to intel in IPC. Where it demolished was in multi cores as you got more cores than Intel. And in a multitasking OS (like any modern OS) it's better to have more cores than less. Why? Because processes can get spread over them. I've got an i7 laptop in addition to this Ryzen 7 machine. When doing things like photo editing and culling, with modern software the Ryzen hardly breaks a sweat. It can schedule processes across 16 threads and hardly ever chokes. Even rendering video it in Resolve it will ramp up and stay there. Work can go on. That is why IPC matters little in a modern system.
Also less than 10% performance and your user will never notice. Ryzen has been in that same league since it came out.
Sure cost is an important factor. Look at a good Ryzen box vs Intel. You get a better, faster, more future proof machine with AMD. You get more cores and lower power consumption. Which means as apps evolve you are in a good position to not need an upgrade. And everyone loves less power and heat.
If Apple truly were "high end" the Mac Pro would have bene done with Threadripper or EPYC. Those CPUs are what Pros need and want.
That's some BS right there. The whole x86-64 architecture is AMD's extension. Nothing needs to be recompiled for AMD. No patches are needed to run stuff on AMD. There are some software that has been heavily optimized for Intel (some math stuff) and some things that works better with Intel's extensions but the software will run fine on AMD. I've been using AMD since the 486 days and never a compatibility issue. There are Hackintoshes running on Ryzen so it's very easy to do.
You are forgetting 2 things:
1. Apple worked with Intel on TB. IIRC they still own a bunch of the patents on it. So they could definitely get it done with TB.
2. ASrock has an AMD motherboard with TB certified by Intel.
ASRock x570 Phantom . If a small OEM can do it, surely Apple can get it done too.
I'd also wager that the majority of users, Mac included don't care about TB. They more care about USB than the edge case uses for Thunderbolt.