Some say it's a western ideology
Self-actualisation simply means 'realizing/ becoming you'. And who you can be, you must be.
But do we really need Abraham Maslow to tell us that 'you want to become you'? Just check in with yourself and see if you desire to do the things that are more you than not. If someone tells John to be more like Patrick, John would instinctively feel rejected and hurt.
You want to become you. It's plain human psychology.
But the human personality is complex and it takes more than just the passing of age for you to become you.
Abraham Maslow wrote in his book, Motivation and Personality:
The human personality...
“...is organised into layers, or depths. That which is unconscious and that which is conscious coexist, even though they may contradict each other. One is (in one sense); the other also is (in another deeper sense) and could one day come to the surface, become conscious, and then be in that sense.” (p 273)
And humans could have weak, rather than strong instincts...
“...his needs, his preferences, his instinct remnants are weak and not strong, equivocal not unequivocal, that they leave room for doubt, uncertainty, and conflict, that they are all too easily overlaid and lost to sight by culture, by learning, by the preferences of other people.” (p 273)
Hence, self-actualisation demands higher consciousness...
“We do have a nature, a structure, a shadowy bone structure of instinctoid tendencies and capacities, but it is a great and difficult achievement to know it in ourselves. To be natural and spontaneous, to know what one is, and what one really wants, is a rare and high culmination that comes infrequently, and that usually takes long years of courage and hard work.” (p 273)
Some say it's selfish
Self-actualising individuals practise healthy selfishness. They are able to recognise unnecessary sacrifices in the grander scheme of things. They know that it is only by becoming their best, can they offer their best to others.
They have a greater need for independence and privacy and are generally more detached to what ordinary people are attached to. Instead, they're concerned with developing themselves so that they'd be able to contribute their best.
Maslow found that his self-actualising subjects “...are in general strongly focused on problems outside themselves. In current terminology they are problem centered rather than ego centered...as contrasted with the ordinary introspectiveness that one finds in insecure people. These individuals customarily have some mission in life, some task to fulfil, some problem outside themselves which enlists much of their energies.”
“In general these tasks are nonpersonal or unselfish, concerned rather with the good of mankind in general, or of a nation in general, or of a few individuals in the subject's family.” (p 159)
“The fact is that self-actualising people are simultaneously the most individualistic and the more altruistic and social and loving of all human beings.” (p 199)
Some say it's stressful
The only possible reason is that they got self-actualisation wrong. These people might have mistook self-actualisation as a process to climb to a high point in society (and often, they already have a fixed outcome and timeline in mind) and to enjoy their best lives (which often translates to the high life). When events happen that hamper/ threaten the achievement of these, they get stressed out, which is contrary to how self-actualising people are.
“One of the characteristics of self-actualising people is their relative independence of the physical and social environment. Since they are propelled by growth motivation rather than deficiency motivation, self-actualising people are not dependent for their main satisfactions on the real world, or other people or culture or means to ends or, in general, on extrinsic satisfactions. Rather they are dependent for their own development and continued growth on their own potentialities and latent resources.” (p 162)
Some say it's flawed
Maslow himself conceded that the hierarchy is not nearly so rigid as they may have implied. Maslow observed that “There are some people in whom, for instance, self-esteem seems to be more important than love” ...then “there are other apparently innate creative people in whom the drive to creativeness seems to be more important than any other counter-determinant. These creativeness might appear not as self-actualisation released by basic satisfaction, but in spite of lack of basic satisfaction.” (p 51)
Maslow also clarified in his book that one level of needs need not be 100% satisfied before the next level of needs emerges. Normally, one is partially satisfied and partially unsatisfied in all their basic needs at the same time, and “...a more realistic description of the hierarchy would be in terms of decreasing percentages of satisfaction as we go up the hierarchy of prepotency.” (p 54)
p.s.: If we agree that we are unique individuals with unique personalities, strengths and talents,
then self-actualisation is a process to honour that and to allow us to become who we can be to be of service to others. And if this is the epitome of success and happiness, is it not yet clear that success and happiness actually take the same work?