It means nothing even if it were true.
Many other religions have been around longer than Catholicism. Do we have to accept them as true too just because they've been around a long time?
Preaching to mules placemarker
But in terms of the Christians of the past: they are His, and because of that, they are ours. We are allmembers of the One Body.
And I do not see in your attitude ("They don't matter") that love for the Body.
But Jesus said He was sending the Holy Spirit to guide the Church (His Body, His followers, His Bride, thecalled-out people, the people who believed in Him) into all truth. Therefore the record of those actual people and how they were guided, is about US, because we are all members of His One Body and guided by His Spirit.
I used to be mighty aggravated by history, because I was a young cynic who just saw history as it's usually taught, as One. Damned. Thing. After. Another.
Then a wise teacher told me that that history is the field of action of Divine Providence. I resisted that mightily, because it seemed patently absurd that Divine Providence had a hand in this mess.
But my teacher persisted: if our history is NOT the field of action of Divine Providence, then there IS no Divine Providence: because Providence can only act in the midst of what actually happened: and history is What Actually Happened.
So, back to our interest in, love for, and concern for all members of One Body.
The eye cannot say to the hand, "I don't need you!" And the head cannot say to the feet, "I don't need you!"
But you have to look at from the perspective of the people who, from age to age, trusted in His Name.
That got me into history again, with a new motive and a new meaning.