Actually we do have guidance from Jesus as to who is not.
You Will Know Them by Their Fruits
Our Lord Jesus Christ said, “Beware of false prophets, who come to you in sheep’s clothing, but inwardly they are ravenous wolves. (15) You will know them by their fruits. Do men gather grapes from thornbushes or figs from thistles? (16)(Matthew 7:15-16)
Our Lord Jesus Christ also said, "And then many will be offended, will betray one another, and will hate one another. 10 Then many false prophets will rise up and deceive many. 11 And because lawlessness will abound, the love of many will grow cold." 12 (Matthew 24:10-12)
Our Lord Jesus Christ also said, ** “Then if anyone says to you, ‘Look, here is the Christ!’ or ‘There!’ do not believe it. (23) For false christs and false prophets will rise and show great signs and wonders to deceive, if possible, even the elect. **(24) See, I have told you beforehand. (25)(Matthew 24:23-25)
Our Lord Jesus Christ informed us about who is not. He even said, See, I have told you beforehand. Our Lord has been generous to us.
In Christ,
Silouan