It's hard to keep up a trained workforce when they lock the doors so tight.
The value in something like Cent/RHEL is LTS stability. Really, the only valuable part of Cent/RHEL is the stable kernel because the userland rapidly becomes old and useless. Something like Ubuntu with a RHEL quality kernel with a 10 yr support lifecycle but without a separate foss/commercial version would be superior to either RHEL or Ubuntu. Canonical went full shark-jumping mickeymouse with their "Pro" subscription and non patching model unless you pay $.
That's also true for a Kubernetes cluster.
It does take some work to accomplish this on more complex apps, though. Things like SQL databases and rabbitmq are very often single points of failure in practice. At smaller companies, it's often easier to stick them on more resilient hardware than to architect an active/active or active/failover system. I agree that this isn't the best way to do it, and IMHO any important service should have HA of some sort.
That said, I use x86 based machines for all my personal projects, and I wouldn't buy IBM systems if I owned a tech startup just because they're like 10x the price of x86.
P-series and mainframe machines have a lot of cool tech, and they're very resilient. They can even lose a CPU or some RAM and keep running. x86 systems would more likely freeze/crash immediately.
But the only reason I know P-series/AIX at all is because one small branch of IBM hired me for my linux skills back in 2011, and I learned on the job. But I quit after 5 years, because the pay wasn't sustainable. The machines are too expensive to play around with otherwise. If you learn by doing (which seems vital to be a good sysadmin or programmer), even a license to use AIX is out of the hobbyist's price range. Training courses are limited lab environments. You won't get nearly as much out of that as you would from a 12-month AWS subscription, or a $5/month VPS, or an x86 virtual machine, or a raspberry pi. etc, etc.
And IBM ended their developer machine licensing. So now employers can't even afford to maintain extra P-series machines for devs/sysadmins to play around with and learn.
But don't worry, IBM will keep shooting their feet off until they no longer exist. There will likely be a panic, similar to Y2K, where everyone's feverishly re-writing and porting and emulating and migrating things off of IBM iron and onto x86 machines.