I'm not really sure what you are arguing other than you have a different setup than I do. Nothing you said suggests that I shouldn't have the number of buttons I do as the game currently is right now. You just configure your UI differently because of using a controller.

I don't use a controller, therefore all my skills are keybound in various different ways on different hotbars than yours are.

In the end you didn't actually argue that the skills aren't used (except some strange idea that most of the role actions are basically useless, I can assure you they are not). You just argued that the skills I mentioned could be configured some way on a controller that has absolutely nothing to do with my buttons in my UI. As I said before, since maybe you missed it, some skills are used more frequently than others, but that does NOT mean that those skills that aren't as frequently used can just be dropped or not configured. We are all still expected to have them available and quickly accessible.

Pots/Medicines: these only matter if you’re doing end-game raiding. Otherwise, they don’t need to be on your bar.
No, that's not the only place these are useful. They are useful anywhere you might get tagged with a silence, such as in Pagos, for example. It's also nice to have potions available for emergencies when a healer can't pay attention to you right away. Not to mention folks that still use placeholder lesser potions in their rotations to keep their muscle memory in their openers.

Duty Actions: Duty Actions can be used with R3/L3 for controller users. You don’t need them on your hotbar—there’s very few fights where they’re used anyways, if you consider all the different duties in this game.
When there is visual spam all over the screen it's a million times more efficient to tap a keybind than to try to find where the mouse cursor is to hover over a duty action button and click it. I can't believe you would even suggest such a thing and that three other people agreed with you. Good for you that you can do some magic with a controller stick. Keyboard users will still have to keybind in some way and that means a button. Therefore ~50 buttons.