A question from a retired, former graphic designer (who's designed, re-designed, and survived the back-and-forth corporate logo approval gauntlet for
"my initial creation, which deserved to be hung in the Louvre" 
)...
What is the purpose / influence behind this recent streamlining or flattening?
From a practical standpoint,
the timing seems illogical. We now have all the bandwidth to go "full Baroque" in detail and nuance. Media-wise, you would expect this to be an era embracing a return to artistry, working hand-in-hand with the deepest understanding ever of human psychology, to produce a second golden age of advertising. Instead, everything seems dumbed down to below 1950s standards of uniform mediocrity.
On the other hand, facing a career extinction event, it does seem timely as an industry to squeeze out one, last paycheck before AI absorbs everyone's job. What better way than to generate a trend that requires immediate response and less creative time/ability.
My impression of this trend is that it's as if human designers were
cooperating in the demise of their jobs, generating a look that serves as a bridge to machine-generated graphic design.
If I was still in the business, I'd be devoting my remaining time to challenging AI, putting out work that's
filled with soul and humanity, humor and nuance, and intelligence that has some historical context. I know, the younger markets are not particularly equipped to receive such. But that's all the more reason to set your customer's product apart as something that aims higher, that appeals to (and thus, imbues its) customers with better than average sensibilities.
(Full disclosure: I was heavily influenced by, and still love, the non-Brutalist, flat, minimalism and typographic playfulness of the mid-60s. But what I'm seeing in the current minimalist trend is very different. It seems
less playful,
less humanizing, and much more embracing of "left hemisphere" and machine-learned sensibilities.)
Now you kids get off my [#117c13 Color Hex] bio-textured plane to horizon vanishing point!