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Instead tell them to choose their favorite social IdP on the discovery interface. This will immediately win over a sizable proportion of your audience who will blithely log into your app with almost zero effort (since most social IdPs will happily maintain a user session indefinitely).
As However, as Jim Fox demonstrated on the social identity mailing list the other day, not all users feel comfortable performing a social login operation. Some users have a healthy distrust for social IdPs, and moreover, that lack of trust is on the rise. So be it.
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If you're still reading this, you'll want to know what the viable alternatives are. Honestly, I havendon't a clueknow. All I can say is that I'm intrigued by the user centric approaches of the IRMA project and the FIDO Alliance. If similar technologies were to proliferate, it would be a death knell for the centralized IdP model. In its place would rise the Attribute Authority, and I don't mean the SSO-based AAs of today. I mean standalone AAs that dish out attribute assertions that end users control. This is the only approach I can see working in a World of Zero Trust.