Who was the book of Hebrews written to? And the book of Peter? It matters. Especially in the matter of doctrine in this age of the grace of God.
They are written to all.
That is a very basic premise of the word of God.
Obviously the entire evangelistic portion of the NT was written to “The Lost Sheep of the House of Israel,” but that always includes those of us that sojourn with them spiritually.
It is not a closed invitation.
There are SO many people here on FR that like to read the NEIGHBOR's mail that the postman accidently places in their mailbox.
Oh; they LIKE the cards from Gramma; with a $100 bill in them; but they toss the electric bills in the trash!