It should be noted: Rand's definition of objectivism doesn't exactly match what you expect from the common sense usage of the word.

I think Objectivism fails because at least in part it doesn't establish solid enough foundations, and takes as fact unproven things that rely on mountains of suppositions and not always reliable evidence.

For example, whatever you think of "laissez-faire capitalism" (as supported by Rand), it's very weird to make its defense part of a philosophy, more so as a kind of axiomatic statement. Imagine someone were deep into some math book, say a dense Algebraic Geometry textbook, and it was just declared out of the blue that "laissez-faire capitalism is an ideal system" or something like that. That could even be true within some context, but I think it's out of place. It also relies on so many assumptions and is far from conclusively proven (the way capitalism is implemented also varies considerably today, and I don't agree that being maximally "laissez-faire" turned out to be better, at least not obviously)[1]. I would even understand she divulged her political ideas, but kept separate from the basis of a philosophy.

Also, like many philosophies, I don't think objectivism survives a closer scientific scrutiny. I suppose there was no firm grasp on what the mind was, or the nature of conscious (there is still some uncertainty, but much more clarity). I like how Dr Rachel Barr (a neuroscientist I follow on social networks) put it: old philosophies, specially about the human mind and soul, made great observations some of which unfortunately (such as that the 'Pineal gland is the principal seat of the soul' as regarded by René Descartes) can be "swept away" and basically definitely disproved by science from a better understanding of the nature of our brains and minds. Some assertions about perception and consciousness seem to be outdated.

I particularly object (no pun intended) to the basis of ethics as individuals. As I've argued previously[2], we now understand the nature of consciousness to, in my view, not justify an ethics that is based solely on the primacy of self-interest. We are part of a giant network of interactions, and although the self seems like a very important concept for our society, metaphysically it doesn't make much sense to prioritize the self at all costs (even when this prioritization includes some strategic concessions for altruism), though I think it's important that we take care of ourselves for pragmatic reasons, because we basically are the ones that understand ourselves the most and live with ourselves 24/7.

I think Objectivism (although again I am no specialist, I haven't studied it profoundly) has merits around notions of reality being singular and shared by everyone in one way or another, and (hypothesis mine) if everything derives from a singular reality, by understanding this singular reality we should be able to in a certain sense understand everything (including ethics, art and morality, which I think is highly counterintuitive) -- because our brains and minds which form the basis of such questions are part of reality, as well as any internal processes within those that enable subjective perception and subjective reality.

I wrote more about this here[3]. Please take a look if you're interested.

[1] Not to mention, we hardly got to try out 2 (or maybe 3) political systems in any serious way: capitalism and socialism (also perhaps social democracy), although there are a myriad of variations to experiment with as well (forms of voting, systems of regulation, the design of various institutions) that aren't considered when talking about "political systems". Who knows if something else could be better? I think a more general view of society as a whole as a kind of giant system is necessary to understand how to design better societies in general.

[2] https://news.ycombinator.com/item?id=43528352

[3] https://old.reddit.com/r/slatestarcodex/comments/1iv1x1m/the... Please see the questions where I expanded a little upon those ideas :)