Nephthys

I fully endorse the OP's UI values. I think my old UI with Discord is a fairly good realization. I used it for raiding. Notable features:

Visual simplicity. Having the unit frames, action buttons, and minimap together in one continuous block makes it easier to find the information they contain, because there's not extraneous background colors or shapes interspersed among them. This is part of the reason people like having the black bars at the bottom of the screen.

The UI I linked could be improved by having the Slice & Dice bar and cooldown reminders better integrated with the main block. I put the minimap in the main block not because I really needed it there, but because it made the UI that much cleaner. Later on I just mapped minimap show/hide to a hotkey so I only saw it when I needed it.

Layout. The information I look at most is as close to the action as it can be without getting in the way: near the center of the screen at my character's feet. This is my main problem with UIs that have everything at the bottom of the screen.

Reminders for abilities that are NOT cooling down. I'm mainly interested in knowing when I CAN use my abilities, not when I can't. Discord allowed you to set up buttons that appear when the ability is ready. That's what the two buttons are above the yellow timer bar. These days I use NeedToKnow for this. PowerAuras can do it, too.