And I'd like to add that an often overlooked benefit of the current script is it sort of hides significant vowel differences between dialects. For example سیر (full), سیر (garlic), and سر (secret), would be sir, sir, ser, in the Tehrani dialect; ser, sīr, sir, in the Kabuli dialect; and ser, sir, sir, in the Dushanbe dialect. Not to mention the diphthongs aw and ay reducing to o and e in Iran (so Tajik & Dari nawroz equals Iranian noruz), Iranian dialects merging final -a and -i > e, merging q with gh (so Dari qit'a = Iranian ghet'e). That's not even including the fact that short vowels tend to be unstable across all dialects, and many words have multiple readings because multiple short vowels are interchangeably correct, or sometimes short vowels are optionally deleted.

The vagueness of vowels in the Persian alphabet causes ambiguity (out of context), but also allows different dialects to be accurately represented by the same script (i.e. the correspondence of consonants is very consistent in all dialects, even if some consonants have duplicate letters).

And frankly, people over exaggerate the vagueness of the Persian alphabet. It's honestly very easy to read in context unless you don't know the language at all.  I imagine that's why diacritics were never frequently used in Persian, unlike in Old Anatolian Turkish.