I mostly agree with Oomis and not with DaasYochid.
I would point out, though, that it’s Lashon HaKodesh, not, lihavdil, “Hebrew”, that we have not changed.
Yeshivish English, as in English interspersed with “Torah learning” words, is, “limaaseh”, far more unifying than Yiddish.
How many baalei bayis learn with an Artscroll gemara or other English-translated work, some of whom would be unable to do so without these English-language works? How does Yiddish even begin to compare, as Oomis indicated?
If anything, Yiddish, today, outside of Chassidic communities, is more polarizing than unifying as it divides between the speakers and the non-speakers.
As well, making Yiddish a primary language along with its attendant downgrading of English also results in certain Jews having an embarrassingly poor command of the English language, which can be a chilul Hashem, CH”V.
For those who do not speak Yiddish at home yet, for various reasons, attend a Yiddish-teaching school, this nostalgic infatuation with Yiddish makes their schooling unnecessarily harder than it already is and they lose out academically versus had they been taught in English.
On the same topic, Jews in various sefardic countries (before the Zionists persuaded them to come to Israel at which time the Zionists proudly shmaded them) have had their own dialects of the local language yet they continued to use Lashon HaKodesh names. From where did some Ashkenazim get this idea that Yiddish is the new Lashon HaKodesh?
I, too, cannot understand why anyone would give up naming their son after Moshe Rabbeinu, the Avos, malachim, neviim, et al. and instead give them a “Yiddish name”.