That sounds truly painful for all the creatives involved. They must be either sad or disengaged. This is obviously a whole different ball of wax than making a copy of TikTok or whatever else they decide to clone, so you just cannot set priorities or judge quality the same way.
It’s sad on a creative level but from a career perspective, many of my friends (from when I worked in film) are earning multiples of what they earned previously, and are doing less work at the same time.
So it’s easy to just give in and do the lowered task at hand rather than fight for the high end work they were hired to do.
It seems more likely to me that they have art directors, they're just the same ones that design the weird corporate advertising art with the tiny heads. It's very "safe" for lack of a better word.
Safe works when you're selling productivity software, but not when the product is (partially) the art/design/environment.
From the evidence, Meta doesn’t have any.