MH does have its roots in Loshon HaKodesh, but its adjustments of it make it the worst of both worlds – since it has Loshon HaKodesh elements we dont want to use it for our mundane purposes – and since it has non-Loshon HaKodesh elements, we do not want to accept it as our national language. So to speak MH is one thing, but to say it is the “language of the Jew” is just not so. Neither is Yiddish the “language of the Jew”, any more than a black hat is the “clothing of a Jew.” But just as the purpose of the hat is “lo shinu es malbushayhen” – we want to dress differently than the seculars – thep purpose of Yiddish is “lo shinu es shemom” – we want to talk differently than the seculars.
There is no Mitzvah to speak in Loshon HaKodesh. Without the modernizations, its not much of a speakable language (we don’t have that many words). And if you do add in a bunch of words and tweak it, youll just end up with another Yiddish, but based on Loshon HaKodesh, which is only a bad thing, not good, as per above. Plus, the Responsa Chavtzeles HaSharon (I:OH:10) writes that Loshon HaKodesh is only Kodesh if its used exclusively for holy things. Once you start using it to speak mundane things, its not holy anymore. It’s like an Aron HaKodesh – once you use it to hold your model racing car collection and not Sifrei Torah, its not an Aron HaKodesh anymore.
In the Sefer B’Tuv Yerushalayim it relates that the Maharil Diskin refused to speak to a certain Talmid Chacham of Yerushalayim because he used to spek only Loshon HaKodesh. Said the Maharil Diskin, “For generations we are accostomed to speaking Yiddish, not Loshon HaKodesh.” He saw in the speaking of Loshon HaKodesh a contradiction to historical percedent, which originated based on the ideas in the aforementioned issues. The Chasam Sofer is in his comments on Shulchan Aruch, OH #65 – the reason we do not speak Loshon HaKodesh is to prevent undesirable people from speaking it, plus to prevent its being used in Tameh places. The posek Hagaon Rav Akiva Yosef Shlezinger in his Sefer Lev HaIvri says we should not change our spoken toungue from Yiddish, and he draws parallels with our usage of Yiddish in modern times, to our usage of Aramaic in ancient times.
What about giving a Shiur or Dvar Torah in Loshon Kodesh? The reason that was not done is because Loshon HaKodesh is very hard to use in a speaking manner – its much more suited to writing. Would you start a sentence with “hinei”? And even when Divrei Torah are writen in Seforim, they add in many Aramaic words and expression, to the point where someone who only know Hebrew but not Gemora language would have a hard time understanding it. There simply aren’t enough words or expressions in Loshon HaKodesh to do that. Its awkward even when it can be done. So since theres really no reason to do it – there is no Mitzvah to speak Loshon HaKodesh – but there is a Mitzvah to understand your learning as best as you can, it was deemed by Klal Yisroel better to use foregn language – or at least a combination of Loshon HaKodesh and foreign language, which is really what is needed to get a complex Torah idea across.
Remember – the Gemora itself was done in Aramaic – a foreign language, and not Loshon HaKodesh. And thats because it was more easily understood. Foreign languages still are. And the point of the Chavtzeles HaSharon by saying that Loshon HaKodesh loses its holiness when spoken for mundane matters was that doing so is a Bizayon for the Holy language and it therefore should not be done. Historical precendent is valid only when the past generations could have done somethign but clearly chose not to. Speaking Loshon HaKodesh was an available option for them just as it is for us – and they could have created a “speaking language” out of it if they wanted – just like they did recently. The fact that they didnt shows that they chose not to. We should, too. But Loshon HaKodesh – with the Aramaic and foreign words mixed in, which is what is used for Torah – is not really speakable. But it woks best from the written Torah word. Its not a coincidence that after thousands of years, those who finally came up with the idea to speak Hebrew were atheist Apikorsim who did it specifically for heretical reasons – because in order to be a “nation” you need a language.