For human beings, they sound like a nightmare.
We're already getting a taste of it right now with modern systems.
Becoming numb to "enter admin password to continue" prompts, getting generic "$program needs $right/privilege on your system -- OK?".
"Uh, what does this mean? What if I say no? What if I say YES!?"
"Sorry, $program will utterly refuse to run without $right. So, you're SOL."
Allow location tracking, all phone tracking, allow cookies.
"YES! YES! YES! MAKE IT STOP!"
My browser routinely asks me to enable location awareness. For arbitrary web sites, and won't seem to take "No, Heck no, not ever" as a response.
Meanwhile, I did that "show your sky" cool little web site, and it seemed to know exactly where I am (likely from my IP).
Why does my IDE need admin to install on my Mac?
Capability based systems are swell on paper. But, not so sure how they will work in practice.