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…
I don't think a manager will be impressed by a report saying "I know you can't do your whole job, so let me handle face time with the execs so I can take your job from you."
If I don't trust them to represent me and the team, then obviously that suggestion wouldn't work, but I'm trying to express the difference between someone pointing out a problem as if the problem is just yours or offering to help take responsibility for the problem as part of a team with you.
I've worked with people who made it a point of pride to always bring a concrete, workable suggestion whenever they brought me a problem. We didn't always go with their suggestion, but they were fantastic to work with.
Thankfully, I've never had to worry about keeping good people on my team down out of fear they'd take my job.