1. Improper Ramp Configuration (includes ski racks on gondolas)
2. Improper Queue Configuration (includes RFID gates)
3. Inadequate Staffing Levels
4. Inadequate Staff Training
5. Guests Unwilling to Pair Up
6. Priority Access (ski school)
7. Lift Running Too Slow (or too fast)
The items on this list run a spectrum between things that annoy me greatly and things that I understand aren't necessarily up to the Operations team at the ski area.
Item 1, (ramp configurqtion / gondola ski racks) usually would require additional capital to fix. That doesn't mean it shouldn't eventually get fixed when funds are available / when changes are made to these areas. But if that takes years to remedy, I don't mind it usually. I don't like it when a new lift comes with these problems, however.
Item 2 (queue configuration) is one of the ones that quality management can typically mitigate for free. A poorly laid-out queue corral can dramatically impact the efficiency of a lift, and generate queues where none would exist. The most common issue I see is when the RFID gates are placed too close to the loading zone. Proper placement can prevent gaps from forming in lines and keep the chairs full when demand is high.
Items 3, 4, 6, and 7 can be the result of factors outside a mountain's control, or be the result of the mountain making a reasonable tradeoff given their operating priorities and staffing realities. It doesn't mean these problems should persist, but I understand that they can't always be fixed overnight.
Regarding item 5 (guests unwilling to pair up), what you say about it is true. However, solving the problem is not very easy at all. When I was in college, I was a ride operator at Disney World, and one of the rides I operated was Spaceship Earth, a continuously-loading dark ride where guests continuously load similar to a chairlift.
At a certain point, the operator needs to make a tradeoff between courtesy and efficiency, as enforcing a "no seat goes empty" in the rapid paced area of the loading zone can frequently end up with more seats going empty, despite efforts to the contrary.
Lift operators should certainly encourage full utilization of the lifts capacity when demand is more than a couple chairs worth. But beyond that, my experience is that enforcement is typically unproductive.