These have been supported for a while now – you're not going to get old browser support, but they're not going to support 3D features either, so your complaint is either flame bait or ignorance.
For Safari still the -webkit prefix is required which is a bit odd
Though, its super unfair that the Web Inspector in Webkit uses unprefixed Flexbox (http://trac.webkit.org revision 173707).
Analytics are irrelevant when you're writing some huge internal service for a company whose conservative upgrade policy dictates that only one older browser will be installed and used company-wide until God-knows-when.
By the way, glancing at a few browser market share websites, it looks like IE8 and IE9 are alive and well, totaling around the same as IE11.
Anyways, centered stuff is evil! http://uxmovement.com/content/why-you-should-never-center-al...
If clean lines really solved the worlds problems, we'd be in much better shape by now.