Telling them that my auth provider isn't out, but the thing I use to show them a blue button vs a red button is.
Oof.
The combination of these two has been all we've ever needed. User segmentation, A/B testing, pilot soft launch etc are all easy.
I have no idea why that is.
I couldn't get anybody else to adopt this software despite putting a lot of work into making it easy to pick up and install.
10 years later competitors popped up like mushrooms and were adopted quickly. The thing they all had in common was somebody else owned your user database. So yeah I feel pretty cynical.
My university had a great shared browser bookmark management system, even with a basic discussion support for them. In 1998. It was not super popular because people just didn't have that many links to share, eventually it fell offline and got accidentally deleted in 2001.