That's really what this is all about. As I said before, this simplistic no-detail design lowers the entry barriers for people who want to be "designers." There are other reason, none of them are good. Fad mimicry mostly.
I do think (opinion alert) there’s some merit in that statement, unfortunately.
In the absence of any examples of how aspects of Big Sur and iPad OS’s flat/minimalist/monochromatic interface fixed interface issues after the “golden age” (~2005-2012), I sadly & truly believe (opinion alert, opinion alert) that the main reasons for the rise of the simplistic no-detail design are based not so much on what was robust for the customer but more due to background forces. Truly, what’s the value (what was fixed that was broken before) by rendering Big Sur’s email app to be all white monochromatic with light-colored low contrast fonts and flat “buttons” that are hardly distinguishable from other neighboring buttons/folders. Fugly and sometimes painful to use when searching for emails in folders, where the less-dominant arrowhead method of showing sub folders is not nearly as clear as before and takes a little more work each time when seeking out a hundred different folders on a given workday.
Three main reasons as I see it (opinion alert, opinion alert), none of them directly based on fixing issues with the then-existing interfaces to improve customer usage.
1) Beavers (have to) build dams, marketers (have to) market, and designers (have to) design. Put a beaver atop the Eiffel Tower and it’ll look to build a damn. After a few years of wonderfully appropriate, engaging, and intuitive interfaces that were refined to the hilt, loved by customers, and envied (and stolen/revised) by the competition, the Marketers and Designers at Apple needed something to market and something to design...something to further separate themselves from the competition’s half-baked iOS/OS clones...something to shake things up and make their jobs interesting (and justified). As Apple’s two defining credos have always been “provide just what (we think) is necessary (for the customer)” and “minimalist industrial design” (translation: there isn’t much low-hanging-fruit of unnecessary extras available to pull out), then what other option to shake things up while staying true to the credo is there other than to look for things to shave away while injecting more minimalist design. This need to actively chase change in existing products is an unavoidable consequence of needing to be fresh and new in order to support expectations of revenue growth when it’s not possible to consistently keep inventing new products.
2) Jony gained more power after Steve died and Scott “left.” Jony got his mitts into the software/interface design. He’d gone on record stating there was too much fluff in the OS’s of the Forestall days. He loved much of the Windows phone’s wafer-thin-font and light blue/white dumbed-down-simplified aesthetic (which, ironically, was a forced invention by Microsoft so as to not pirate iOS so blatantly directly like Samsung did back in the day). He’s gone on record being painfully jealous of the minimalist Yahoo weather app (which, in place of white clouds, yellow suns, and blue rain drops that provided a near-instantaneous assessment of the upcoming weather were instead thin-line-outline simplistic representations that took a little more concentration than before to quickly assess the week’s weather ahead). In less time than it took for some OS refinements, he radically reinvented iOS into his vision in under a year, birthing out a half-baked iOS7 full of reinventions (in the absence of any proof that any of the iOS6 interface elements were broken or failures, and fixed by the radically-reinvented interface iOS7 elements).
3) The world follows Apple design, even off a cliff sometimes. If Apple does it, it must be good, no? If Apple does it, then I want it in my website or app or else not look up to date. Apple does it, then others copy and it proliferates. If it’s proliferating, then it must be good, no?