And today the answer to that question means "maintain a very large and dynamic dataset of the world's written languages" which makes it unpalatable to "low level" software, like the standard libraries of every PL that I'm aware of.
If Arabic text editors don’t have the cursor behave the same as English ones, that’s fine. If I press backspace in a Hebrew text editor I probably want it to delete the character to the right. The behavior doesn’t need to be universal
Now add to that the fact that nobody wants to build a new editor for every single language, and there you go - all of that gets rolled into a common approach. It's hard to impossible to get right. (Because what you want also depends on context, not just language - URLs demand different behaviors with BiDi than text does)
Even if we wanted to build different editors, as soon as you start quoting things not from your preferred environment, guess what, you have mixed environments and need to start thinking about BiDi
It's a gargantuan mess. Nobody is really getting it right, we're just trying to get closer and closer. (And if you want to see folks in the field pulling out their hair, mention you'd like Boustrophedon writing ;)
Source: UAX 9 and UAX 29 were printouts on my desk for several years, for very good reasons. I still have unsolved problems with BiDi text, I've just given up.
I suspect you might be over-indexing on the specific example of emojis and skin tone modifiers that the article used, but on the Unicode implementation level that's just the same modifier characters that several real languages need to use to be encoded properly. It's not a useless frivolity.
Funnily, in the case of English, that would likely mean replacing the latin alphabet with a more complicated script. Because in contrast to e.g. German and Italian, that script really does not fit its phonetics very well. Hell, even Japanese romanization, "romaji", makes much better and more consistent use of the latin alphabet than English. Which is just all kinds of funny to me, English is so bad in that regard, that Japanese, a language which is very far away from English in multiple ways, can make so much better use of the to it foreign latin script. In fact, English is so extraordinarily bad in using the latin script, that the English-speaking world even has literal contests about how to spell pronounced words, called "spelling bees".
And yet I see no real efforts to simplify that gaining traction.
Most of the so-called complexity in English is just about scoring "style points", it's not necessary to communicate (other than the admittedly huge vocabulary - again a result of its formation from multiple influences).
The irony is English is simultaneously the best and worst option. It can incorporate things from almost any other language while making spelling them correctly impossible. Good luck memorizing adjective order and the nearly infinite number of idioms. A lot of them come from British sailors.
The whole point of Unicode is to encode languages. We already handle Arabic, which means we should be able to handle most languages. Even if we can’t convert a language into codepoints, we have the ability to record sound and images in resolutions beyond human acuity.
You’re right the technology dictates form. The computers represent English different than print. Due to the limitations of previous technology, indented paragraphs are less common than an empty line between paragraphs. Same with single-width or double spaces after periods.
In my experience, the complexity comes from the reality of how we write in different writing systems. I think this is inevitable.
Emoji don't introduce any edge cases of their own. If your software can't join a skin tone to a thumbs up, it also will fall apart on composing many scripts used by hundreds of millions of people.
So if you really want to get all kids-these-days about emoji, go ahead, but support Unicode properly. You'll get correct emoji handling as a consequence of that anyway, and you can still signal whatever message you're intending to send here about yourself in some other way.