Ok hold on now. If I said "it's a different time, we have different spiritual needs", you'd be calling it modernism. I understand that "thou" signifies closeness, but so does the Spanish "tu" which Tradhican condemns. "Thou" back then and "tu" in Spanish or "du" in German today are basically identical in meaning, and yet he's alright with the 1855 Missal's choice to use "thou" but not the use of "tu" in Spanish Missals. God does not change, so there's no reason why we'd need to refer to Him with different levels of closeness or formality depending on the decade of our birth. If "tu" today is wrong, then so was "thou" in 1855.
Spiritual truths are eternal and unchanging. Spiritual needs vary according to individual and culture. Modernism wrongly attempts to treat spiritual truths as changeable, but nobody here is saying anything like that.
God does not change, but the world does. We live in a post-VII, post-NO world. There is Communion in the hand while standing, the altar rails removed, felt banners replacing statues of Saints, shunning of Latin in liturgy, virtual disappearance of Gregorian chant. This list could go on, but I hope this is enough to give the idea.
All of these things and more are attacks on the sacred and our ability to have a sense of the sacred. Anything we can do to hold onto the sacred is something that we ought to do.
As the word "thou" is used in English today, it is special language for worship. It is sacred language, not common. And that is why we should prefer it.
By 1855, "thou" was no longer familiar speech. It was already hieratic speech as it is now.