The things around us have become plainer. In 1923, or 1823, the fashion was for intricate and richly ornamented architecture, furniture, clothes, dishware, or whatever else. In 2023, fashionable objects are plain and minimalist, if not outright utilitarian. Steve Jobs believed that every object should look as much like a featureless white sphere as possible, and the rest of us follow in his footsteps.
The obvious counterpoint is that there many modern streetlight designs that are quite elegant. You chose a particularly disgusting streetlight as your example, but if you go to many newly developing cities you can see streetlights that may not be as charming as some antiquated ornamented lights, but they are also not blatantly offensive like the one in your example. That streetlight must've been purchased either by a city planner that despises other people or purchased during the 2000s (a dark time when the world was being flooded with disgusting designs at a pace unprecendented in human history, e.g. look at the best-selling cars from that era, then compare it to the previous decade or the decade after. What the hell happened?).
You can't even blame functionalism for that disgusting streetlight, since as you said, it ignores "the attention to aesthetics found in deliberate minimalism." A streetlight designed by Apple product designers probably would not be such a bad thing (as long as it didn't force me to sign in using my Apple ID).
If you're making a stronger point that a well-designed modern streetlight is inferior to a well-designed ornamented streetlight, I'm not sure if I entirely agree with that. But I do agree that even the most well-designed modern products have an inescapable sameness to them that diminishes the aesthetic personality of the thing, especially for public architecture and design.
The more fundamental aesthetic problem seems to me to be why there are no longer any distinct cultural features reflected in the general design of our personal and public spaces, which you touch on in the footnotes. The usual explanation other than the ones you offered is that the sameness is the result of globalization. An architecture firm employing a multinational team educated in multiple countries using standard textbooks and course material probably has 1) many of the same ideas as everybody else, and 2) they have to make a large degree of compromise even if they all have culturally distinct design ideas.
There are some famous counterexamples like the Xi'an International Football Centre (https://i.imgur.com/ukroPXA.png), but this is an expensive custom design that only works in a place already present with a highly developed aesthetic history. What happens in places with no cultural distinctness or aesthetic history? Trying to imagine a distinctive Texas football stadium is basically impossible. What even is Texas architecture? The closest thing is maybe old cowboy towns with semi-temporary wooden buildings. A football stadium in the style of a saloon would feel like a theme park at best and an oversized hipster shack at worst. A stadium in the neoclassical style like the Alamo would be even more comical. It would look like a giant McMansion with vestigial McMansion pillars. Would slapping on more ornamentation really fix the fundamental aesthetic problem? I don't think so.
That gets to the broader political problem. A country like the US is an assimilationist culture that also proselytizes under the liberal universalist dogma that all men are created equal. It's contradictory for a country such as the US to pursue distinctive cultural features while at same time trying to subsume the world under its cultural hegemony. The reason why people in cities all over the world watch the same movies and listen to the same music and wear same clothes and read the same news and even care about the same hot-button issues as Americans is that the US culture and media industry has been able to mass produce totally non-distinct, one-size-fits-all, globalized cultural products easily consumable by masses of people of all different backgrounds. In other words, if American culture were more distinct, it would be less attractive to non-Americans, and the US culture industry would not be able to exercise as much subjective control over the world. As long as American ideas and its mode of cultural production predominates in the world, that feeling of sameness, of Apple-ness, is also bound to remain.
Yes and no. The fact is that to a large extent the market is determined by those who buy in bulk. If something can be made on a small scale, then enlightened consumers can support its production even in a world gone mad. But things that require major capital investment rely on the major bulk-buyers patronising them. The more concentrated production is in a few hands, the more this holds true. Real estate companies prioritise cost and convenience because once they sell it has nothing to do with them any more, and boring things are (a) as a rule, cheaper (b) have wider use because they 'fit' everywhere. Obviously, public authorities don't care about quality. Fixing this requires changing economic incentives so that the preference of the overwhelming majority of people for ornament is reflected in the market system. Also, we need to kill all architects.