Vincent, I would say that one reason for your “success” with DCS is really the handheld throttle, where there are buttons and screen information telling you what you are doing.
You are working with a system where there is one manufacturer, so everything works the same, push the dedicated whistle button and the horn/whistle sounds.
All the more advanced systems have the capability, but the user interface is the key to making it fun.
In DCC sound for example, lights, horn/whistle, bell, sound mute, brakes are pretty standard. So is momentum, but few people change it during a session.
You can further “define” your own standard, and you can do it with different manufacturer’s decoders, which is nice, so if you are a coupler clank person, or a cab chatter person, you can customize it to your liking.
So, for simple speed control and direction and horn/whistle and bell, dedicated buttons make sense, and if you are using a smart phone, you can make the “buttons” big enough to hit easily (although you still have no tactile feedback and have to look at the phone).
But as the requirements to do things like smoke on/off, cab chatter, coal shovelling, coupler crash, adding “load” to increase the “working sound” of the loco, as the need/desire for all these things increase, then throttles with dedicated buttons become simpler than digging through menus or remembering weird, non-intuitive keystrokes.
Look at the evolution of word processors on computers, they used to be all keystrokes you had to remember, now most people don’t even know the cut and paste keystrokes, they hit the “menu button” with the mouse.
Greg