So a popular theory in the pronunciation of Hebrew is that "Biblical Hebrew" (or, at the very least, Hebrew up to the point to the fall of the Second Temple and well into the 8th century CE) had pharyngeal pronunciations for certain letters that are lost in modern Israeli Hebrew today. The ayin was actually an "3ayin" where the letter is pronounced as a pharyngealization of which ever vowel the niqqud shares. The teth is not just a "T" sound, but rather a T with this constriction with the pharynx. The same with the tsade as well, as it is actually an "S" with the same constriction as with the teth. Some scholars dispute this and claim that these pronunciations came later and were borrowed by South-West Semitic languages (namely Arabic) while many others claim that these were common pronunciations 2000 years ago.
However, if this is the case, then how come there is no "Dad" in Hebrew, Syriac, and other Levant languages? The "Dad" is just that some pharyngealization that is done on the consonant "D," so why does this letter only appear in South-West Semitic languages (once again, namely Arabic)? If a people could pronounce "Teth" "Sade" and "Ayin" as pharyngeal letters then wouldn't it be pretty simple to also pronounce a "Dad" as seen in Arabic? Is it fallacious to think it's weird that the "Dad" should be expected in Levant Semitic languages? Does this show problems with theories of pharyngeal letters in Semitic languages (and that these letters of Hebrew and Aramaic alphabets actually changed pronunciation due to Arabic influence)?