There are more mediocre organizations than there are bad or great organizations, which makes sense given the definition of mediocre. Mediocre organizations “get by”, and there are many people who are totally content with that type of culture. It should not be thought of as bad, if the team members are content and are a match for the leadership and culture of the organization.
However, in a high growth environment, mediocrity is intolerable. It is not just a problem for those that lead; it is also a problem for the team members that are go-getters, because they too will not tolerate deceleration.
The happiness of individuals and the leadership of an organization is more about the FIT. It would be unwise to join a high-growth team if the individual is more comfortable in a less growth-oriented environment, just as it is unwise for Leadership of a high-growth organization to tolerate demotivating others by accepting mediocrity.