What is this latest web UI fad going on?

I've noticed a trend in web UI design. I'd like to know what this kind of website is called and why it exists now. I would also like to ask why at least two websites with this new trend, Chase Bank and B&H Photo, are so bad. It's almost like the designers have forgotten the first principles of UI design in their rush to incorporate some fad technique.

The predominant visual feature is that everything is a big rectangle. Fonts are big, buttons are big, text fields are big.

There is more dynamic movement and change. Things appear and disappear individually, rather than entire pages loading and reloading. For instance, the "Okay" or "Go" button will be grayed out until all the fields in a form are filled in, and then it will become active. Menus are more dynamic and context sensitive.

There is a circle "spinner" kind of thing that spins while new pages or sections of pages load.

Now for my complaints.

These new websites break password managers and form-fillers like LastPass.

These new websites have excessive animation. I might be alone here, but I believe that a good UI should use animation judiciously. Otherwise it's distracting and makes it harder to focus on the essential information.

These new websites have no consideration for the layout and flow of the information on the page. Over the years of using computers I have come to expect that there is some kind of master menu at the upper left, a menu that gives choices at the highest level of context. Then as you move your eyes down and to the right, you expect to see more context-dependent menus and information.

Well, chase.com disregards this completely. There are menus all over the page, with no rhyme or reason. On the same page you might see a menu triggered by the icon with is a stack of horizontal bars, another one elsewhere on the page triggered by three stacked dots, and another one labeled "Things You Can Do." (I just love that, "Things You Can Do".. thanks for being so specific!) There is no sense for how these menus relate to each other, or whether they are context-specific.

chase.com uses these dynamic "Take action" buttons that stay grayed-out until you fill in all the fields. Some of those fields are optional, but the button will remain grayed-out until you place the cursor in each one. Basic UI problem.

The buttons you use to take action could be placed above, below, or to the right of the information you are acting on, which no rhyme or reason.

Information is terribly disorganized on both B&H photo and Chase.com. On the checkout page at B&H Photo, it asks me to review the order. Information that is not important will be in a huge font, while information that is essential to verify, like my address, will be in a very small font. My address is put on one line instead of three lines like any normal human would do. There are checkboxes that look normal, and then there are these huge green checkboxes on the same page, with no rhyme or reason. There's no "flow" to the information, nothing guiding my eye over the essential steps.

So, is there a reason why these new-fangled websites are ignoring basic UI principles?