Is it still the correct decision if I do not have a 20% down payment (or even a 5% down payment)?
Depending on the real estate market and your specific property, a monthly mortgage payment has a good chance at being lower than comparable monthly rental payments. Bear in mind: every dollar paid for rental is burned, whereas every dollar paid to a mortgage has at least some potential to be recovered in the future. And think a few years out: say you pay $800/month for rent. Over three years, that adds up to $28,800. If you live in a hot area, your rent will likely increase, so you'll pay more in the long run. A mortgage payment, however, will not, and you might get that $28,800 back through renting it and/or selling.
I see renting vs ownership as "XaaS" vs in-house. Renting is essentially Housing as a Service. There's a use case for XaaS, but at a certain point, owning critical infrastructure just makes sense.
Oh, I know it's very difficult for poorer people to buy property. Are you familiar with land contracts (also called contract-for-deed)? In certain scenarios, they provide a path to ownership for poorer people, but they're also offered in a predatory manner.
I'll add that a poorer person seeking to buy might consider moving out of a big city to a smaller town. Obviously, this approach isn't for everyone. However, if home ownership is that important, you can find nice homes for sub-$150k in many smaller towns. At that price, a 30-year mortgage is under <$1000 a month. Considering how much a two- or three-bedroom apartment may cost in a big city, financially, it works out.
It is financially advantageous to own a property, it is usually financially advantageous to own a property if you purely want to rent it out - renting is a profitable business that's why there are a lot of really large companies holding insane amounts of property in the US. If the city/region has some guaranteed demand for rental numbers (like uni stundents and young people working their first job) then the math changes to make it even more advantageous to rent - what you're essentially seeing is that owning property is the correct decision, it's so correct that the market for property is being soaked up by landlords that can make a tidy profit on the margin and are more reliable load recipients than individuals.
I'm sorry you're in the housing situation you're in because it sucks but, if you did see two identical places you liked and one was available for sale and the other for rent then it'd be the correct financial decision (really correct in fact) to buy the property.
Various regions within the US have toyed with ideas around taxing property ownership for investment more heavily but there is a lot of lobbying money pushing back on that. A lot of places (including BC where I'm at) actually have a primary residence tax credit for owners - if you own your property and use it as your primary residence you get a bit off your taxes to help swing the balance back toward individual owners.