Example: giving feedback is notoriously hard, even if it's really clear what the issues are. Promotion is also hard (you have to choose who to promote and who to not promote), and most of the time you do know the right choice but you might not be able to call it for personal reasons.
So yes, if you happen to manage people, spend a LOT of effort on self-reflection. Go to a coach, therapist, go to courses where they let you practice and where you get feedback. Whatever works for you, just keep investing. Also, don't worry if the coach, course, therapist is imperfect.
Promotion is hard because as a manager you don't have the power to promote. There's HR on top of the organization deciding every year that there's no budget for raises and no slots for promotions.
When you're finally allowed to promote someone for real, after many years of tenure, the 10% raise is pale compared to what they could get by joining a new company.
So some of the promotion dance may be more complicated in larger orgs, but it’s still hard in other orgs since it’s a value judgement on merits earned and as with all value judgements, there’s no absolutely correct and mathematically defensible formula.
It's 90% about what they could get somewhere else in the city and a bit whether they are willing to leave and capable to (it's actually quite difficult to get a job ^^). You should have a pretty good idea of the what's available in the area after a while.
As you noticed, everybody think they deserve more. Ironically everybody is wrong, because the fact that they work here for this amount is proof that it's enough (for now), if they could get paid more they'd be paid more (whether here or somewhere else).
The key is to ignore people because people are always dissatisfied. Big companies set a fixed pay band and reply to everything with "there's no budget for a raise" because it's the nice easy way to do that.
Promotion is 'hard' because there are very few spots to be promoted int to, it's a narrow pyramid, and people generally want to 'increase responsibility and salary' when that isn't consistent with the reality of the situation.
Feedback is hard because people tend to take it personally.
The entire piece is misguided in the sense that, although toxic managers do exist, it's generally far more complicated. Different situations, different people, different levels of expectations, differing levels of legitimate authority, emotions vs. outcomes etc.. Some people perceive 'loudness' to be problematic, some people don't care (see: inside of a hockey locker room).
Usually focusing on material things, outcomes etc. matter, the rest is not that important. Personally, I try to have a huge latitude for tolerance of different types and don't care that much otherwise frankly. Truly diabolical patterns of behaviour like back-stabbing, not taking ownership of failure - this kind of stuff is quite bothersome - and those behaviours can come in 'nice happy bosses'.
Why not worry about that?
Because one will still pick up enough useful things, for it to be worthwhile? And if changing to a different therapist or coach, that one will probably also be imperfect?
(Assuming the therapist / coach isn't really bad of course.)