When you are maximizing square footage and are limited by building codes for the type of construction (almost always wood frame with sealed panels for the exterior) you get a box. They also use the maximum amount of land so there’s no grass to mow or places for people to use, so you get a big box on a postage stamp because that’s the cheapest way to get the most retail space.

I would guess the new designs are more of a money thing. Someone probably figured out an improved floor-plan design that somehow "increases productivity, and profits" so now various corporations are jumping on the newest gimmick bandwagon to "increase productivity and profits." It's not uncommon for corporations to perform monkey-see, monkey-do, copy-catting of each other, if they think it will earn them a few more pennies.

Brutalism.

The best example I can think of is Starbucks. It used to be a typical warm coffee shop. Now all the stores have an empty barren design. Same for McDonalds, Wendys, Panda Express, and any other franchise.

Culture is going minimalistic and void of life. As if not to offend anyone or inspire. Blank. Dull. Empty. Dead. It is reminiscent of communism.

It's a tactic of communism. Destroy and replace with drabness

The boxiness might come down to space efficiency and streamlining. I imagine it's trickier and more expensive to install HVAC and wiring in buildings with rounded corners and such.

Yes, very weird. A lot of buildings get torn down really quick then replaced. Certain strip malls have been vacant for decades and suddenly they are gone. I am waiting to see what they put up. Probably FEMA camps.