the real world is orders of magnitude more complex than IT.
I agree. Even a regular accountant's job today is far more complex than the everyday open-source perfectionism. I've tried many times to move entire accounting departments to open source. Everything failed, literally everything. Modern accounting is one of those areas that's 100% tied to proprietary code. The code can be poor, buggy, cumbersome, and unoptimized. But then the tax authorities, social security, and pension funds come calling, and so on ad infinitum. And then the accounting department becomes overwhelmed with proprietary software and technologies.
You could create an open-source PC and people will complain it is more expensive than a bargain bin mass produced Dell.
Yes. I agree. I was offered an Operasor smartphone. It was several times more expensive than the average mass-produced Samsung. Of course, why buy something like that? I didn't understand and still don't. I don't work for a secret service. A regular PC with a reliable FreeBSD is enough for banking.
[you had to explain your understanding of that]
I hinted. I thought you'd guess... trivial
K.I.S.S.
Keep things simple, and it makes em easier to manage over-time!
Yes, the K.I.S.S. principle is becoming a thing of the past. Everything is becoming more complicated.
Possibly, this is the force that keeps humanity moving forward.
"no one is going to tell me how to do things this time."
This mechanism only works on localhost today. As soon as you start reaching the "middle atmosphere" with institutional structures, things get completely fucked up.

I can't work with the tax service, the emergency services, the hydrometeorological center, etc. today, only on an open-source platform.
They're all under proprietary standards. They're part of the state machine. You can't force them or convince them otherwise.
Even here, many people use proprietary platforms. That's just the way things are. They won't be able to fulfill the manifesto, even partially.