TLDR: This was actually a good read. While I disagree with some points (more on that below), I think on the whole it points to a big problem: The trend is unsustainable. The growth in assets (specifically land prices) have grown faster than the economy as a whole and are the main driver of inequality. This is due to housing appreciation which itself is driven by increasing demand but a strict supply of land. We need to adopt policies that transform housing from a class ripe for speculation to a cost center. Housing appreciation is great for the owner because they sell at a massive profit, but a detriment to everyone else.

The article looks like it supports a French economist called Thomas Piketty and his book Capital in the 21st Century. In it, he makes a truly frightening prediction observation: The returns of capital are growing faster than the economy as a whole. The article explains what he means but copying for convenience:

Piketty's argument is that, in an economy where the rate of return on capital outstrips the rate of growth, inherited wealth will always grow faster than earned wealth. So the fact that rich kids can swan aimlessly from gap year to internship to a job at father's bank/ministry/TV network – while the poor kids sweat into their barista uniforms – is not an accident: it is the system working normally.

This is precisely what the article the OP posted is about. If the economy grew by X%, capital grew by X+Y%. Inherited wealth accumulates faster than the general economy and if left to continue, it would eventually dominate the society. Another economist, Rognlie, built on Piketty's paper and found that the increase is not evenly spread throughout all of what Piketty calls "capital" (in OP's article, the "the financial and housing markets"), but specifically housing. There is some debate about the exact value of increase, but both Piketty and Rognlie agree that it is increasing. Per the article:

Once you factor in depreciation, Rognlie finds that across a range of developed countries the rise in the capital share of income has been modest. What's more, it is entirely accounted for by the housing sector rather than by the kind of business investments — factories, office buildings, equipment, patents, etc. — that put the capital in capitalism.

We need to tax the driver of inequality, which is housing, specifically housing appreciation. When a relatively affordable $200k house appreciates to $1 million over 10 years, it's no longer affordable. But why did it appreciate in the first place? It's certainly not because the building got any better. In fact, the structure is almost certainly worse for 10 years of wear and tear. This appreciation came from the land values going up and leads directly to the concern both Piketty and OP brings up.

So how do you fight the increase in land prices? By making it a poor investment. Land (raw land--the lines on a map) has a few characteristics that make it unique:

• It's required to be able to live/sleep/eat/work/do anything
• It's non-fungible and the total amount is static
  • You cannot substitute an acre from the middle of nowhere for an acre in downtown
• Its value is primarily a function of what's around it
• It's cheap to hold

Because of this, you could give people more money but it would just end up going to rent/pushing housing prices up because the issue is systemic. We can see this today if you look at somewhere like San Francisco or Manhattan where salaries are quite high but only the people at the top can afford a home. As a result of the scarcity and limitations, it attracts speculation like is discussed in this video which further drives up prices because now a scarce resource is even more scarce. And likewise, that wealth accumulates over time as it is passed down between generations.

The only solution is to change one or more of the properties: We need to make it costly to own property while simultaneously making it easier to build. The mayor of Detroit has a presentation about precisely that and IMO is well worth a listen. He's described literally every city I've ever been to. From Seattle, SF, LA, DC, NYC, Raleigh, Vegas, Nashville, you name it. In any of these cities, you can walk downtown and easily find vacant lots, surface parking lots. Here's an example in my city: a whole block of parking lots downtown worth $20m that could be built on but instead is waiting for someone to pay them off so they can build. There's a lot of land that is taken out of supply that could be built on but is left underutilized! In my city (Raleigh), there are about 1,300 acres of privately owned land held vacant totalling in the billions of dollars. Why? Because it makes lots of money when someone else wants to buy and build on it.

Housing (specifically the land it sits on) should not be an investment that appreciates freely on its own. It should be a necessary cost that gets paid so people have no incentive to hoard it or keep it out of use while every incentive to use it to its fullest potential. However, the incentives we have today (zoning + property tax) makes it one and actively encourages hoarding and speculation. Only by changing that will we be able to make not only affordable housing, but keep it affordable. And by doing will we be able to address the inequality issue.