To OP, St. Pius X said that the proper pronunciation of Latin is the Italian method and encouraged everyone to adopt this.
Until that time, there were a lot of differences from country to country–so much so that at Vatican I there were “translators” of “French Latin” into Latin properly spoken (the Italian method) so that the fathers of the council could speak to one another.
These pronunciations still exist and are still viable systems of pronunciation. “Properly spoken” is biased unless by it you mean “properly spoken according to Italian pronunciation.” Even St. Pius X (if I’m not mistaken) only specifically encouraged the use in the Liturgical setting or when dealing with matters related to the church. Thus it is not the only “proper” pronunciation, but rather, is itself only proper in certain situations. If I’m mistaken about St. Pius X’s statements, please direct me to the quotations I’m wrong about (I don’t mean that to sound rude or insolent; I’m actually just interested

).
Fortunately, St. Pius X set things straight.
While not personally a fan of Italian Latin as the be-all, end-all of Latin pronunciation, I must commend St. Pius X on his part in helping to get rid of English Latin . . . it truly was disgusting as far as I’m concerned.
The “classical” pronunciation was devised by German secularists in the 19th century with a purpose to sound un-ecclesiastical (though some of their arguments seem to hold for the way Latin was pronounced, say, in the Golden Age). This is part of the reason it sounds strikingly like the German pronunciation of Latin.
That’s not entirely true. It may have been derived by German secularists, but that has nothing to do with it. The point was not to make Latin sound un-ecclesiastical, but rather to see how close to Latin (as it was spoken by Romans) the current systems of the time came. Two completely different things. And for the record, while it may have started out strikingly close to German (I’m not up to date on the history of Classical Latin reconstruction through the past couple centuries), it is certainly incorrect to say that of the Classical pronunciation taught now. Besides, the sources for Classical pronunciation are far from biased toward any nationality or religion; we have the writings of the historical Republican and Imperial grammarians themselves discussing nearly every facet of the language’s pronunciation. Hardly “some of their arguments.”
It is important to note that the proper Italian pronunciation does not simply mean the Italian way of speaking Latin with an accent from your particular country (e.g., aspirating h’s or making any notice of the h’s at all, for that matter). The h is entirely silent and is never noticed, whether it is at the beginning or middle of the word with the only two exceptions being mihi and nihil for the reason noted. Well, the reason is that the pronunciation developed that way for those words, which is why they can sometimes be found spelled michi or nichil.
Again, that’s not a valid argument. Many words had alternate spellings, but these two are
older (read as "archaic at the time of the Empire) spellings of the words. The overwhelming majority (if not all) spelling variances at the time of the church’s founding in Latin dealt with vowel changes that make no sense in the supposedly “correct” ecclesiastical pronunciation. For example, “optimus” was often spelled “optumus” by native speakers. The * and of ecclesiastical Latin would not allow for such a variance. However, *
Edit: (Is this showing up as lowercase to others? It should be an upper-case “I”)* and ʊ] respectively (which the ancient grammarians reference as sounds) do allow for such.
I simply do not see the reason behind forcing one contrived and unfitting pronunciation system over other contrived and unfitting pronunciation systems. Besides, the Latin you speak of that was spoken in Tuscany was itself a derivative of Vulgar Latin, not the Latin which the church uses (they really were almost completely different languages, much like is slowly happening with English in public speaking versus everyday conversation). So even if the progeny of Italian pronunciation is 100% from this Tuscan period, it’s based on a completely different system than the one it claims to be.
Edit: To put it in terms of the English language: Beowulf was written in (for sake of argument, though I know we can’t pin it down) 800 AD. Chaucer comes along some 500 - 600 years later speaking Middle English, which is a derivative. He picks up Beowulf and begins to read it as if it were pronounced like Middle English exactly. We then freeze this pronunciation in time until modernity and use it exactly and perfectly. Yes, it’s an old pronunciation, but it’s still an incorrect pronunciation. It’s the same thing with the Church’s Latin. The pronunciation system of the Italians ultimately traces back to high Latin, but this does not mean it is the same.*