Note that “lack of consistency” is only bad when independent companies or end users are doing it. When Apple itself makes software with a UI nothing like the non-themable look and feel of macOS, no one complains.
Fun fact: non-themable UI is the first reason why I don’t use macOS. Not the most important one, but first in the list.
I just got to reading the post about booting Windows XP or not, and I remember how many people say “Windows XP looked silly”. The default “Luna” theme looked silly. Windows XP looked the way you wanted it to look.
I think there’s quite a difference between making the user feel empowered and actually empowering the user. Also users have different needs so empowerment (as well as feeling empowered) looks different for everybody else.
My notion of empowerment is when the computer assists me in doing the task I set out to do, and then reliably so. I have nothing from an infinitely customizable UI and cutesy non-features when I can’t connect my bluetooth headphones or can’t get graphics to work reliably. That sounds like a false dichotomy, but my experience has been that software that allows you to turn less knobs works more reliably in its core functions. That also intuitively makes sense to me as a developer.
Dark mode, to me, is also not in any way related to themeability, it’s an accessibility feature. The difference being that you only allow the level of customization that people with varying needs need to have to be able to read things better. Not as a means of self-expression.
I feel the same level of nostalgia towards old computers the OP feels, but I did not feel more empowered back then than I do now, just perhaps more excited and entertained. I dare you to install any of those old things in a VM and attempt to use them. I have done this and the anticipated sense of empowerment fades very quickly. It’s a good way to validate your memory too.
You can have this same experience in 2021 if you write GUI applications using the FOX toolkit. Applications look like Windows 95, and you can use the FOX control center so that all FOX based applications have the same theme and colors.