I'm looking for single sign-on solutions for a set of internet facing web apps we currently own. I was vaguely aware of ACS a few years ago and it was highly hyped by Microsoft. Recently as I've been digging in to single sign-on solutions it has become evident to me that ACS seems to be taking a back-burner with Azure AD now at the forefront. On top of that I see that Google has made moves that take Google Sign-on out of the picture for ACS.
So I'm wondering, is ACS still relevant? Is it on the downward slide? Would I be making a mistake to tie my apps to it now if I decide it is the right option for me?