Sure, it may take a decent amount of intelligence to learn all the intimate details of the philosophy and to gain a highly developed understanding of it and its applications on the level of say Leonard Peikoff. However : One need not aim for this level of understanding in order to understand the basic tenants of Objectivism and to be able to apply them to ones life. This is not the same as blindly accepting what O'ism has to say, and it does require a fair bit of learning and thought, but I do not think it is beyond the intelligence of anyone that does not have serious mental problems. Anyone with a reasonable amount of intelligence should be able to eventually and with varying degrees of effort , be able to understand O'ism well enough to successfully apply it so that they can think more rationally and live their life in a moral way.
An Objectivist is someone that understands O'ism and attempts to live their life according to its principles. But those principles involve not blindly accepting what O'ism has to say and in fact understanding to some significant extent what Oist prinicples mean, what facts give rise to them and their implications to ones life. That is what understanding (according to O'ism) involves, the ability to comprehend why a given principle/fact is true and how to apply it in the correct contexts.
Anyone can pick up O'ist principles and apply them blindly, and it may help them to some extent. An Objectivist on the other hand has a reasonable understanding of Objectivism, he knows why its principles are important and how and when he should apply them. Again, anyone without serious mental issues should be able to eventually get to this point ( it can ages, trust me) with more or less effort. Nothing in O'ism is all that difficult to grasp if one studies it in the correct order, it all deals with fairly fundamental facts which relate to things which one can easily observe ( at least if one knows what to look for ). So I dont see why it should require any great intelligence to be able to apply it to ones life to some degree of success. The extent to which this happens depends on to what extent one is able to connect ones experiences etc with O'ist principles, but for most cases in ones life, this should not be too hard if they really get O'ism and train themselves to think properly ( O'ist material helps with that too).
I would like to add as as an aside : Anyone that thinks they have a *deep* understanding of O'ism and that thinks they understand the roots of all / many its principles without years of study, is almost certainly wrong about how much they actually understand. It is actually a lot harder than that, as simple as it may seem at face value.
Alice doubts what she sees and feels for most of her time in Underland. She repeatedly declaims that it is all a dream despite the fact that pinches and painful pinpricks do not wake her up, and that she cannot be hurt in dream but the bandersnatch draws blood. Denial of the independent existence of the world apart from the mind is what is what solipsism is. The blue caterpillar named Absalom is described as "Absalom is absolute", and eventually brings Alice around to accepting the reality of her surroundings and her own memories. The story shows Absalom is right, Alice has spent most of the story being wrong and even stupid.
The Red Queen is a stand-in for the premise of the primary importance of emotions: she has usurped the crown from her sister the White Queen, has a heart for her symbol, often bursts into red-faced shouting and considers her dilemma to be whether to it is better to be loved or feared by her subjects. The White Queen is the legitimate ruler selected by her parents to inherit the crown, passing over her older sister the Red Queen. The White Queen is pale and colorless, always calm and constrains her behavior to conform with her (unspecified) vows. The story plainly casts the Red Queen as the villain and the White Queen as the victim. The Mad Hatter is mad it seems because he teeters between the two poles of emotional outbursts and reasonable discourse. The Mad Hatter's character supports the conclusion that reason and emotion are actually the sides of a dichotomy, as he is the only character who attempts to combine the two elements and is a failure (driven Mad) because of it.
Alice is emphatic in insisting to the dog Bayard that she sets the course of her life (actually her "dream" at this point in the story) in deciding to rescue the Hatter from the Red Queen. When Alice feels pressured to take up the Vorpal Sword and slay the jabberwocky, the White Queen counsels her that she should not live by other's wishes but choose what she does freely, for she will be alone in her conflict. The dilemma in the "real world" framing story shown before Alice falls down the rabbit hole and after she comes back out is resolved with the exercise of a bit of willful courage on her part. Alice is a non-conformist and comes to a happy conclusion at the end of the story. These incidents approvingly show the role and importance in life of willful activity, of volition.
