If Christians relied only on Luther you might have a point. Fortunately we have the original texts to compare our translations to.
“Fortunately we have the original texts to compare our translations to.”
No, we don’t. No one does. There is not a single autograph of any Biblical book known to exist anywhere in the world. What you just said is OBJECTIVELY false. All we have are copies - and even some of those might be translations of copies.