What if I don't want to live in an apartment most of my life?
c.f. https://www.youtube.com/watch?v=iGbC5j4pG9w
[+] I realize that number is surprising, and I would have found it surprising up until ~3 weeks ago, but I can assure you that this product is presently commercially available in Tokyo, including to people who do not exactly smash Japanese banks' definition of "desirable client."
For every apartmemt complex that gets built, that is X many LESS people who are competing to buy that suburb house that you love.
The suburbs will still exist. But more appartments in the city means that prices go down for everyone.
Ignoring that as a rational choice for many people already in expensive areas is just asking for your proposals to fail.
We very frequently talk about the economic value that could be produced by different housing actions, but policy is not purely determined by economic value. I know more people opposed to upzoning because they like their yards and their space than because they're worried about their property values (denser cities in the US are very rarely cheaper).