It's worth mentioning that a lot of modern architecture (in single family & small-to-mid multifamily developments) is essentially dictated by money: what sells the best (typically the design that maximizes square footage), what is cheapest to build, and what is capable of passing for a given state and municipalities zoning and building code.
People shop by location, price, and square footage as their primary search criteria. Safe & bland architecture with no unique craftsmanship reflects the fact that these things are not relevant for the financing, construction & sale of most housing.
Edit: a few other things to consider.
1. Our relationship with the outdoors has shifted considerably since the invention of modern heating and AC. This has implications on modern architecture.
2. Our relationship with our housing (namely, how many hours we spend in what parts of the house) has shifted immensely in the past century. This has vast implications on modern architecture and construction.
3. The average person's relationship with art and beauty has completely changed in just the past few decades. Consider a pre-war world with little-to-no television in the average household, where you yourself had to look in the world around you and decide what was beautiful; versus the modern world where you open your smartphone and scroll down an instagram timeline or a pinterest board (or watch a show on HGTV) and instantly have an idea of what's "expected" from a "good house". Mass media (including social media for the most part) has a homogenizing effect on culture.