Most of those examples (not giving enough direction, not training new hires enough, not being clear enough on priorities) are probably not going to be surprises for the person, and if you give feedback that shows you want someone to behave differently without having given some thought about why they aren't already then your feedback talks more about your own lack of experience and empathy than anything else.
To give good feedback to anyone you need to understand something about the pressures and challenges that they are facing. And remember that everything is a trade off. For example, perhaps they're incredibly busy, and would like to spend more time with new hires, but are struggling to find time because they aren't getting enough blocks of concentration time to work out clear priorities and they have been told they need to give their trusted colleague more opportunities to grow so they delegated it to someone.
Most likely, if you think something is a problem then they do too. They don't need to be told that or criticised for it, they need help solving the problem that causes the problem.
Imagine the difference between "I want to give you feedback that you aren't spending enough time with new hires" vs "I know you've been wanting to spend more time with the new hires, why don't you take them for lunch and send me to your status meeting over Tuesday lunch time this week."
As I started doing more leadership, I became aware that a lot of the things I might previously have cited as predictable examples of leadership incompetence causing problems were not surprises to leadership. They knew that this course of action would cause problems. The reason that they went ahead anyway was because they believed that the problems caused by the other courses of action available to them would be worse.
Of course, there are situations this advice does not apply, maybe the leader genuinely is clueless or evil or mistaken about the severity of a problem, but a good leader when presented with a problem elsewhere needs to start from a position of respect and learning and if you want to give advice to a leader you should start by trying to model good leadership yourself.