I think this peaked some time around 2015. Back then, I remember many developers getting up in arms about following Apple's guidelines to a T, or insisting that Android apps look like a hyperactive stack of colorful paper cutouts under a direct light.
Since then, I think many of us have gotten tired of looking at overdesigned sameness that by now we all know will age quickly. Programmers no longer see the sense in chasing a perpetually changing visual standard for no reason other than "BigCo said so". Most importantly though, BigCos in question have fallen out of our good graces, and the "Design Systems" they keep pushing are now regarded as nothing but cynical branding exercises that come at the cost of UX.
Maybe in 5 years one or two of those BigCos will be humbled by an upstart, or the state, or the market, or a previously humbled BigCo (cough Microsoft). Then, by necessity, their design systems will become once again driven by the needs of actual users and developers. That's the underlying pendulum.
I'd bet on the next UI standard being a cross-platform library. Electron-like, but with much more efficient stack, and with binding to multiple languages.
I'd bet on "if you can't beat em', join em". Reactive component-based architectures a la React/Vue have won. The DOM has won for the view layer too. And with wasm, you get your bindings to multiple languages. See: Blazor (it's just the first, more are coming). As for desktop apps that could benefit from proper concurrency, lack of a browser sandbox, full system access, etc. - server side Blazor is quietly pioneering a weird new paradigm - essentially running a headless browser in a regular process with full privileges, and then only doing vdom diffing inside the browser.
As a front-end dev, I'm not entirely sure I agree with that. The DOM has some annoying performance limitations, and I'd love to be able to use something better for rendering. I think what the DOM has shown, is that cross-platform and the ability to easily do custom look and feel are crucial.
the push isn't (just) about homogeny of look, it is about consistency for users. When your UI design is backwards (or even inconsistently backwards, such as when a user is in he-IL locale) or you label your Delete button OK on platforms where the user doesn't expect that, it makes using the app frustrating, inefficient, and error-prone
Since then, I think many of us have gotten tired of looking at overdesigned sameness that by now we all know will age quickly. Programmers no longer see the sense in chasing a perpetually changing visual standard for no reason other than "BigCo said so". Most importantly though, BigCos in question have fallen out of our good graces, and the "Design Systems" they keep pushing are now regarded as nothing but cynical branding exercises that come at the cost of UX.