First, what he calls "the desktop era" wasn't so much a desktop era as a Windows era - Windows ran the vast majority of desktops (and furthermore, there were plenty of inconsistencies between Windows and Mac). So, as you point out regarding the Win32 API, developers had essentially one way to do things, or at least the far easiest way to do things. Developers weren't so much "following design idioms" as "doing what is easy to do on Windows".
The web started out as a document sharing system, and it only gradually and organically turned over to an app system. There was simply no single default, "easiest" way to do things (and despite that, I remember when it seemed like the web converged all at once onto Bootstrap, because it became the easiest and most "standard" way to do things).
In other words, I totally agree with you. You can have all the "standard idioms" that you want, but unless you have a single company providing and writing easy to use, default frameworks, you'll always have lots of different ways of doing things.
The Windows I remember was in some ways actually less consistent than what we have now. It was common for apps to be themeable, to use weirdly shaped windows, to have very different icon themes or button colors, etc. Every app developer wanted to have a strong brand, which meant not using the default UI choices. And Microsoft's UI guidelines weren't strong enough to generate consistency - even basic things like where the settings window could be found weren't consistent. Sometimes it was Edit > Preferences. Sometimes File > Settings. Sometimes zooming was under View, sometimes under Window.
The big problem with the web and the newer web-derived mobile paradigms is the conflation between theme and widget library, under the name "design system". The native desktop era was relatively good at keeping these concepts separated but the web isn't, the result is a morass of very low effort and crappy widgets that often fail at the subtle details MS/Apple got right. And browsers can't help because every other year designers decide that the basic behaviors of e.g. text fields needs to change in ways that wouldn't be supported by the browser's own widgets.
Now that all we do is “experience” a “journey,” it’s more about the user doing what the app wants instead of the other way around
That's overemphasising the differences considerably: on the whole Windows really did copy the Macintosh UI with great attention to detail and considerable faithfulness, the fact that MS had its own PARC people notwithstanding. MS was among other things an early, successful and enthusiastic Macintosh ISV, and it was led by people who were appropriately impressed by the Mac:
> This Mac influence would show up even when Gates expressed dissatisfaction at Windows’ early development. The Microsoft CEO would complain: “That’s not what a Mac does. I want Mac on the PC, I want a Mac on the PC”.
https://books.openbookpublishers.com/10.11647/obp.0184/ch6.x... It probably wouldn't be exaggerating all that wildly to say that '80s-'90s Microsoft was at the core of its mentality a Mac ISV, a good and quite orthodox Mac ISV, with a DOS cash-cow and big ambitions. (It's probably also not a coincidence that pre-8 Windows diverges more freely from the Mac model on the desktop and filesystem UI side than in regards to the application user interface.) And where Windows did diverge from the Mac those differences often ended up being integrated into the Macintosh side of the "desktop era": viz. the right-click context menu and (to a lesser extent) the old, 1990s Office toolbar. And MS wasn't the only important application-software house which came to Windows development with a Mac sensibility (or a Mac OS codebase).
One reason so many single-person products are so nice is because that single developer didn't have the time and resources to try to re-think how buttons or drop downs or tabs should work. Instead, they just followed existing patterns.
Meanwhile when you have 3 designers and 5 engineers, with the natural ratio of figma sketch-to-production ready implementation being at least an order of magnitude, the only way to justify the design headcount is to make shit complicated.
The bigger issue I see with "got to keep lots of designers employed" problem is the series of pointless, trend-following redesigns you'd see all the time. That said, I've seen many design departments get absolutely slaughtered at a lot of web/SaaS companies in the past 3 years. A lot of the issue designers were working on in the web and mobile for the 25 years prior are now essentially "solved problems", and so, except for the integration of AI (where I've seen nearly every company just add a chat box and that AI star icon), it looks like there is a lot less to do.
Most people only uses one computer. Inconsistency between platforms have no bearing on users. But inconsistency of applications on one platform is a nightmare for training. And accessibility suffers.
As a sibling commenter put it, previously developers had "rails" that were governed by MS and Apple. The very nature of the web means no such rails exist, and saying "hey guys, let's all get back to design idioms!" is not going to fix the problem.
This eroded on the web, because a web page was a bit of a different “boxed” environment, and completely broke down with the rise of mobile, because the desktop conventions didn’t directly translate to touch and small screens, and (this goes back to your point) the developers of mobile OSs introduced equivalent conventions only half-heartedly.
For example, long-press could have been a consistent idiom for what right-click used to be on desktop, but that wasn’t done initially and later was never consistently promoted, competing with Share menus, ellipsis menus and whatnot.
This feels like the root cause to me as well. Or more specifically, the web does have idioms, the problem is that those idioms are still stuck in 1980 and assume the web is a collection of science papers with hyperlinks and the occasional image, data table and submittable form.
This is where the "favourites" list and the ability to select any text on a web pages came from.
Web apps not only have to build an application UI completely from scratch, they also have to do it on top of a document UI that "wants" to do something completely different.
Modern browsers have toned down those idioms and essentially made it "easier to fight them", but didn't remove or improve them.
<button>Click me</button>
You can definitely do so, it's just not obvious or straightforward in many contexts.
> building for modern desktop platforms is horrible, the framework-less web is being used there too.
I think it's more related to PM wanting to "brand" their product and developers optimizing things for themselves (in the short term), not for their users.