A lot of the facets of leadership are created from the small details of how the organization "automates" itself.
Consider meeting planning, for example. How frequent meetings are, how long they are, how many people are involved, what the meeting venue is, and how the agenda and format is set.
There are all sorts of knobs to turn just in saying "what a meeting should look like" that will impact the flow of communication, and different teams in the same organization will tend to have different meeting styles, but at a high level, the planning has to include considerations around how to allow different teams to interact effectively, since those are the bottlenecks where the information tends to get siloed.
And then you can turn to hiring, assignments, training and promotions and there's a similar kind of thing, where the same person in a slightly different role may be hugely more or less effective, and defining the problem differently changes the kinds of assignments and skills needed. Who creates those definitions, and how? It's not necessarily the manager those employees report to that's creating them.
In fact, there's a whole cascade of effects that come from the macro situation that end up translating into differently defined roles: different legal and regulatory requirements, education and training standards, minimum wages, healthcare coverage, labor organization efforts, etc. The same people in a different country may be happier and more effective.
So, while the manager is the biggest factor in the equation, it's not all on them - it can't be. Some ways of doing business and types of company culture will work in some scenarios and others will not, and the marketplace has an evolutionary tendency to just make random permutations of management style until it finds one that doesn't die, even if it creates a toxic environment. In that light, "effective" management is a highly relative thing and can be encouraged or discouraged by the broader shape of the economy.