Maybe that’s the issue? Were you instantly proficient with the keyboard and mouse?
The benefit of a (good!) HOTAS is having everything you need at your fingertips. These are inspired by the cockpit of fighter jets. Why don’t they use a keyboard and mouse there? Because it would hit you in the helmet if you flew upside down! And it isn’t a universal interface. The cockpit is designed to do one required set of tasks as efficiently as possible.
There is absolutely a learning curve. When someone gets over that, though, you can instinctively do the thing you want. They develop muscle memory and act before conscious thought.
It’s like a car with a touchscreen interface for the radio versus buttons and knobs. They both get the job done. In many ways the touchscreen is more flexible. But in my car where I’m familiar with those buttons and knobs I can change the volume, switch tracks, change stations, and use the cruise control without devoting significant mental energy - or attention! - thinking about how.