Not true.
Zionism can be found in early Sephardic literature such as Yehuda haLevy and Ramban. Modern Zionism’s flaws are “entirely a prod­uct of Euro­pean ideas”.

And, by the way, European Zionists were the ones who really despised the Yiddish language.

I always liked the Oriental versions of Hebrew: Iraqi, Syrian…

Both Sephardic (the true one, not the one spoken in Israel) and Ashkenazic Hebrew are far from Biblical Hebrew.
When comparing both — especially Ashkenazic — to related languages, such as Classical Arabic and Assyrian Aramaic, this becomes really obvious.

In Oriental Hebrew:
*there are differences between Tav/Thav with/without dagesh
*between Tet and Tav
*Vav is Waw (like in Arabic and Aramaic)
*3ayin (like in Arabic and Aramaic)
*7et and Khaf are not the same
*Aleph is a full glottal stop
*Seen and Samekh are not the same
*He sounds like an H
*Gimel with/without dagesh — hard G or like the Arabic/Aramaic letter Ghein or Jeem
*Qoof and Kaph are not the same
*Resh is thrilled

The Sephardim even today pronounce koph and kaph differently, while the Ashkenazim pronounce them the same. Yiddish uses only koph; kaph is reserved only for Biblical usage.

Koph, is, of course, the same as Latin Q, while kaph is Latin K. Latin C, on the other hand, is an Etruscan variant of gimel.

The letter “tav” denoted originally a strongly aspirated T phonem, which in Aramaic palatalized into similar phonem as in English “thing”. That is the reason why the Hebrew alphabet has both “tet” and “tav”; “tet” denotes an unaspirated, normal T phonem.

The [th] phonem has a tendency to palatalize into [s] in speech. This phenomenon is called “seseo” in Spanish language — the European Spaniards pronounce “c” and “z” as [th] while the Latinoamericans pronounce it as [s]. In the Ibero-Romanian stem language in the Dark Ages, the Latin C phonem, which originally was pronounced as [k], became first [tch], then [tsh] and later [th] like Hebrew “taav”. It is not that Spaniards had lisp, it has been like that since the Middle Ages!

The Ladino language, “Jewish Spanish”, which is the same for Spanish as Yiddish is for German, has retained all the Medieval Spanish six fricative phonems, while Modern Spanish has only two.

My own first language, Finnish, has experienced this shift too. The word for water, “vesi”, used to be “veti” already in the 13th century. That is why we still have words like “vetinen” (watery) instead of “vesinen”.

That is also the reason why the Sephardim celebrate brith and Ashkenazim have bris. The final [th] has transformed into [s] during the centuries.

Secondly, that Sephardic/Israeli pronunciation is closer to ancient Hebrew is something there’s no reason to believe. Yes, the stress was probably more like Israeli stress, but we can be sure that, like Ashkenazic Hebrew and unlike Israeli Hebrew, there were pronunciation differences between kamatz and patach, segol and tzere, and tav with and without a dagesh. That’s why, as you put it, when a word” ends in a ‘t’”, someone might pronounce it “like an ‘s’”.