Like what exactly? What's missing of value?
> but this was rarely done in Arabic
Because it's redundant. I know it's frustrating for beginners to guess the diacritics on the words but once you get to intermediate/advanced proficiency level of the language, you'll start to appreciate this design aspect of the language.
> Again, the “current system” in use for centuries in Middle Turkic and early modern Kazan Tatar and other Kipchak languages did not mark most vowels with the use of diacritics in spite of their theoretic availability.
How's this Arabic's fault?
To be honest with you, I am not really familiar with Ottoman Turkish let alone other Turkic languages and their evolution journey but if they didn't make any use of extended vowel diacritics or worse the baseline package of Arabic, I don't know exactly how they managed to communicate using that system.