The key word here is "Wall Street". And this statement is playing off a popular misconception around corporate investors buying up American houses. There has been a bit of a panic around "Investors buying up all the property!!!" With people often citing Black Rock and Blackstone as the main culprits. But most of the "investors" buying up property are individuals purchasing investment properties. Here's an article on…
Controversial, but for affordability reasons, there even should be a cap on how many homes an individual can own for rentals. For the sanity in the housing market, members of society need to be driven to participate in other business activities for income/revenue, not rentals.
Landlords owning property is not a problem. Some people prefer to rent - they may be students, or they may not anticipate being somewhere for long, they might not want the risk of owning a home, lots of valid reasons. Having housing available for these people is good and landlords are a necessary and valid part of this market.
The problem is when people who want to own houses can't afford them, even when they contribute meaningfully to society. The root cause of this is not landlords existing. It is wealth inequality. A vanishingly tiny number of people own almost all the wealth in the system, to a point that the additional wealth gives them no real benefit, but serves only to remove that wealth from the vast majority of otherwise middle class people.
If you want to fix this problem return the top tax tiers to what they were 50, 75, 100 years ago and the problem will be severely reduced. It's not sufficient to solve it, but its low hanging fruit.