You say that as if it's about ARM. Plenty of ARM chips on mobile side - none of them come close to Apple mobile performance. Maybe I'm missing something but it looks like Apple has a good chip design department and I don't see how this translates to other ARM devices - Microsoft had their surface with Snapdragon and AFAIK the performance/usability was nowhere close.
That sucks for Intel but is fantastic for everyone else.
Other vendors using ARM chips means virtualization becomes easier between platforms. Linux servers are going to be running ARM soon with Amazon etc designing their own chips so web devs will want to be ARM native.
AMD can essentially take the high end x86 market and dominate gaming alongside Nvidia GPU's and others can experiment elsewhere!
Nothing good comes from one company owning the entire pie. You create conformance with apple's chips you're subjugating software to apples monopaly whims.
I realize that just having a lot of RISC-V hardware options available isn't a guarantee that they're particularly good in terms of their price-power consumption-performance tradeoffs, especially in comparison to ARM (the "whole universe of high-quality hardware designs" that you mention). That may well have more of a delay.
Apple does not need to dominate the PC market to make money. What they deliver pushes other competitors to improve.
I, like the commenter I've replied to, can't believe that we're even able to frame a processor power shift like this in a bad light. It shows companies they can build something big without x86 - that's good for hardware in the long run, irrelevant of whether it's Apples variant or not.
It's our responsibility, as enthusiasts, to make sure legacy lives on. Plenty of people are building emulators, making home networks with old hardware.
It would be much easier if Copyright/Patents expired shorter after the big money has been made. Things should become open source to let everyone in after the inventor has reaped the benefits of their creation.