We tried libertarianism. It doesn't work. I realize the futility of trying to explain this to someone with the username "rothbardrand" but I used to be a libertarian and I finally broke out of it, so maybe this will give someone else teetering on the edge some things to think about.
1. Libertarianism sweeps negative externalities under the rug. Air quality, noise pollution, the costs to society when an elderly person goes bankrupt. The counter arguments are thin. If you don't ban building in a flood plain, people will build in the flood plain. Then the flood will happen and we'll all be worse off.
2. Libertarianism is inefficient because it demands that people become experts in a wide, wide array of topics in order to be healthy and financially secure. Sometimes becoming an expert in a topic is to experience it. For example, I used to be addicted to nicotine. It's one thing to explain with words how addictive it is, it's another to actually be addicted. By introducing a bit of a nanny state we can use laws and taxes as a kind of cross generational memory and save people from having to learn some of the lessons we had to learn.
3. Libertarianism doesn't address the concept of power. It pits the whole world through the lens of rights when there are other concerns like foreign citizens owning portions of companies critical to our national security or owning large portions of our media.
4. Libertarianism underestimates how much work the state puts towards fighting international crime. We use the financial system to track where mafias hide money and how they organize their money laundering schemes.
The problem with leaving libertarianism is that after years of thinking about everything through the lens of rights and the individual one is left with the question "well, what matters then?" and the answer is difficult, but here is my best shot:
The world is one of consequence. So when think about policies we should be concerned with our ends, but we should choose our ends as if we didn't know who we were in the world beforehand.
So my answer is roughly "consequentialism tempered by individual / human rights".
You don't get to buy into Uber's round because they aren't a public company. If they become a public company they have to open their books. Why? Because widespread fraud happened before this and it wasn't just to little old grandma. Sorry about the violation of your rights, but if I didn't know who I would be beforehand, this is what I think would lead to the best average outcome.
As for the middle class not being able to invest in the best companies, I agree with you that we should change some of our regulations. I agree that the rich are getting richer because not enough companies are going public. Let's fix the regulations that empower investment banks at the expense of the entrepreneurs and potential investors, and while we're at it let's raise taxes on the super rich and close their loopholes.
But at the same time let's acknowledge something else: The middle class and the poor have it best in countries like Sweden or Switzerland or Canada where we have more government not less. Where we have more international cooperation not less. Where we have more "collectivism", more education, more consumer protections, more environmental regulation, more investment into research.
And yes we also have rights too, but they're not these absolute mathematical truths and it doesn't mean we should let a bunch of people skirt fiscal regulation by raising a bunch of money anonymously with ICOs.