But when "thou" was introduced, i.e when the first Catholic English translations were being made, "thou" was not a sacred or special term at all. It was the same word as was used for friends, children, and even animals. If we had a word with a similar meaning today that was substituted in, you can bet any money Last Tradhican would be calling it the height of disrespect and borderline blasphemy. To quote him "So we should talk to God informally, like we talk to nobodies?". At the time of the 1855 Missal, the more formal, solemn term would've been "you". So by his logic, he should have a greater problem with the 1855 Missal than with the new one.
At the time "thou" was first introduced, it signified the close, loving relationship we have with God. And that was a good thing to do at time, in a culture in which this truth was obscured. (This is shortly before the rise of Jansenism, which saw God as very distant from humanity, to point where it developed into heresy.)
But that was a different time. The language was different and spiritual needs were different. We live in a culture that has lost the sense of the sacred. The word that better addresses that need is "thou" not "you". The connotations of these words in the past is irrelevant.