For a while, Arabizi was wildly popular and universally used on feature phones. When mobiles became smarter, it was used less. Japanese has romaji and Mandarin has pinyin. Arabic's Arabizi would increase literacy rates and solve all these digital problems.
The vast majority of Japanese and Mandarin speakers are also not in favour of replacing their current writing systems (which give them a link to thousands of years of their own history) in favour of simplified systems. I suspect it is the same for Arabic speakers.
Romanization is a separate issue to using fixed glyphs.
There was a theory in the XIX / early XX century that full literacy was impossible without the Latin script but such claims are ridiculous especially for Arabic which is an alphabetic script already. China has higher literacy rates than Vietnam, for example.
I don't think the many composition rules of Unicode are really necessary, though. Maybe as an extension for academic work or artistic compositions but not for computing.
If all we had were movable types, all of these language users would find a way to write their language that wouldn't require a Turing-complete computer on each glyph. Now the Unicode gods pander to some of these computer-hostile scripts making the users of different scripts feel slighted.