It's easy to be a back-seat driver. You give advice when you can focus on a single decision, with all the information on your lap. You don't get the blame if it goes wrong.
(It's even easier if you're giving advice in hindsight).
It's very difficult to do it when you're alone at the wheel, facing a big junction with multiple options, limited time, horns blaring from behind, and confusing signals.
You can teach someone the signals, how to perform the actions, and the options available – but it's not until they get out on the road and experience the big junction moments that they really begin to master this work.
The more you experience the moment, the better you become at ignoring the blaring horns, identifying the signals that matter, and selecting the best option – without being overwhelmed.
New community professionals are going to make mistakes at junction moments. You can teach the signals, the actions, and the options, but you can't teach the moments. That's just sheer experience.
Gradually, over time, you learn from your mistakes. You make a mistake, realise it's a mistake, and don't do it again. Those are valuable lessons. Like most skills, the more junctions you deal with the better you become.
It's counter-intuitive to fire someone at the junction moments, that's just part of the learning curve.