And yet, all the English Bible translations from back then used "thou" and "thee". Similarly the Germans always used "du" for God. In Latin, Hebrew, etc. there's no distinction between formal and informal versions of the 2nd person singular. Most languages with a distinction use the informal version. A notable exception is French, but there's plenty of usage of "tu" for God even in French dating back centuries.
https://en.wikipedia.org/wiki/T%E2%80%93V_distinction
I'd also question the assumption that "thee" and "thou" are formal in modern English. They're just archaic. No one addresses a President or King or anyone as "thou"(it's Your Majesty, not Thy Majesty). People only do it with God because they're referencing old translations, which is perfectly fine of course, but to act as if saying the general "you"(which is used both formally and informally in modern English) is disrespectful when in fact "thou" and "thee" were brought in when they were informal, is just plain wrong.
I have in my hands a 1966 missal, I went to look up the opening of the mass, the beautiful Psalm 42 which converted me, and it is gone. Totally eliminated. So I'll go elsewhere to give examples of "you" and you tell me if a king was ever addressed as this?
O God, You give us life again
And Your people will rejoice in You
Show us Lord Your kindness
And grant us Your salvation
O Lord hear my prayer
And let my cry come to You
Take away from us our sins O Lord, we beseech You...
We beseech You, by the merits of your saints....