You do realize that, for 1100 years, the Church ran a whole country of its own: the Papal States. And none of those 1100 years could be termed a Golden Age, or even a Silver Age. The best it ever got there is when the reigning pope forgot that they even existed, because when he did remember, it was no party.
And also that we did indeed have clerics that were politically engaged, to the point of being head of state, as was the case of Msgr. Jozef Tiso, president of the Nazi puppet state of Slovakia.
Sorry, but the Church’s record in political involvement does not inspire much confidence in theocracy. It was a wise decision to recognize that limitation and forbid priests from holding public office.
The other thing you take for granted is that the public will acquiesce to theocratic rule. This is exceedingly unlikely. Revolution would be the most likely response.
As a Catholic, I have absolutely no desire to live in a theocracy, Catholic or otherwise. I doubt very many Catholics do.