“95% of the Catholics I’ve met have no problem accepting all mainstream Orthodox and Protestant denominations are Christian.”
Well, those 95% of Catholics you have met are much more charitable than I am. There are a number of “mainstream Protestant” denominations that I think are open to question. I have sat in some of them. I’d go back if they would show me an annotated Bible, with all the parts they no longer believe lined out and the new things they now believe added in with underlining. I know you will find a vast number of writings of Paul they reject and I fear that there are a number of words of Christ, Himself, that they are ashamed of.
Their ears seem to itch for preachers to tell them comfortable things. I think I read something like that somewhere.
Proof is required of your claim.