You can't beat decades of experience designing CPU cores within just a few years. Come on. The ISA itself is relevant to an extent, but not *that* much.
Companies don't have experience designing CPU cores, engineers do, and engineers are mobile and don't suddenly forget everything when they change companies.
The first part of this answer looked like I may have not detailed what I meant by a company having experience, which would have caused misunderstanding, but the rest of your answer seems to indicate that you actually kind of got what I meant, and somehow assume that all it takes to design successful tech products is a few engineers (however talented they are) that have participated in designing one in the past.
That's a cute tale, but that's now how it works. Yes, a company gathers "experience". Of course, ultimately that's the work of engineers, but that's the cumulated work of hundreds of engineers over several decades. That's precisely why AMD, or Intel can launch a new series of chip every year with very significant performance improvements. That's iterative improvements, for sure. Not the work of just a few engineers alone. And no single engineer can possibly have in their head the entirety of that accumulated knowledge. They are using and re-using blocks that others have designed before them, and iterate over that.
That misconception is actually rather common and a common cause of many startups crashing into the wall. Delusions of individual grandeur.
Look at just one RISC-V company, Tenstorrent. CTO Jim Keller is an industry legend. He was instrumental in Intel's Ice Lake and Lakefield CPUs and before that in AMD's first Zen cores, not to mention Athlon (K7) and then Opteron (K8/Sledgehammer) 20+ years ago. In between he was at Tesla and Apple (A4&A5). Tenstorrent also has Wei-han Lien, lead architect of Apple's M1.
Good for them. You're again overestimating the power of single men to redo from scratch what has been built over a very long time.
Apple M1 is sure a great piece of engineering, but it's largely built upon ARM stuff. That's absolutely not like desiging new cores from almost scratch.
And I also mentioned, incidentally, patents. AMD and ARM have thousands of active patents, Intel tens of thousands. Not talking about Apple. If you're below the radar, they probably won't care whatsoever what you're doing, but if you are becoming half successful and start threatening (at least potentially in the long run) their business, rest assured they'll look at what you did very closely and if there's any hint that some patent may apply, that's going to be a rough ride. Especially if you've worked there before. So, there's quite a bit of stuff you won't be able to reuse. Even when they seem like original ideas.
Utlimately, I don't really get what you had to say against my previous post. As you acknowledge in later posts that getting there takes time, which was exactly what I was explaining. Yes, a company gains "experience" through the work of its engineers over the years, that serves as a basis for newer developments. Otherwise all companies in the world would just be empty shells. Fortunately, that's not - quite yet - the case. And however great an engineer you are, and however you think the company you have worked for owes you everything, reality often strikes back when you try achieving the same thing in a brand new startup. You may realize that you were not alone working, after all, and that not everything was in your head. Just a few thoughts for what I think is relatively obvious.