I didn’t mean to suggest they aren’t still fairly common, or that they can’t be made well. I’ve just noticed a trend of them becoming a bit less common in the past few years, but that could always be some combination of the specific brands I follow closely and the fact that my background is on the opposite end of the MTB spectrum (enduro/gravity/DH).
I didn't know they were ever used much in the enduro/gravity/DH world, but they are a mainstay in the XC world and for good reason - weight savings and cost savings. Santa Cruz and Transition moving to flex stays just kinda cements that platform.
Not saying flex stays are all that great, but they are here to stay and are gaining more traction every year. You might even see them in the trail/enduro space before too long.