This was broken with Ribbon and the hamburger menus that every application seems to have switched to for no other reason it seems than to copy Chrome.
To be fair Ribbon is somewhat useable again, but the in the first version I have no idea how people were supposed to find the open and save functions :-)
Other problems:
Tooltips are gone. Yes, I can see they are hard to get right on mobile, but why remove them on desktop while at the same time when the help files and the menus were removed?
The result is even power users like me have to hunt through internet forums to figure out how to use simple features.
Back in the nineties I could also insert a hyphen-if-needed (I have no idea what it is called but the idea is that in languages like Norwegian and German were we create new words by smashing other words together it makes sense to put in invisible hyphens that activates whenever the word processor needs to break the word and disappears when the word is on the start or in the middle of a line and doesn't have to be split.)
Back in the nineties I was a kid on a farm. Today I am a 40+ year-old consultant who knows all these things used to be possible but the old shortcuts are gone and I cannot even figure out if it these features exist anymore as documentation is gone, tooltips are gone and what documentation exist is autotranslated to something so ridiculously bad that I can hardly belive it. (In one recent example I found Microsoft had consistently translated the word for "sharing" (sharing a link) with the word for "stock" (the ones you trade).
Hamburger menus I disagree with but sort of understand the logic of - they're basically like making 'fullscreen mode' the default mode, and then the hamburger menu button just sort of temporarily toggles that off. It makes perfect sense on mobile (I don't think that's what you're talking about though), and on the desktop it can make sense in a web browser when you have, essentially, 3 sets of chrome - you have the desktop window, the browser's chrome, and then the website's chrome all before you get to the website's content.
Some platforms publish a list of recommended guidelines which are effectively a standard. For example here's one from Apple about when and how to use charts in an application: https://developer.apple.com/design/human-interface-guideline...
Also they were called GUI standards or UI at the time.
The modern equivalents called UX isn't reflecting the same conglomeration of standards and conventions though. So not talking about the newer stuff.
I'm no expert on it, and it required specialized expertise. It's been abandoned for mobile interfaces and the modern UX stuff, which often optimizes for design over functionality.
If you've never used old software, it's hard to explain. But old Apple or Microsoft GUI standards would cover the basics, but you'd also need to study the applications and how they presented their GUI.
Nowadays man's applications are web apps, build without such frameworks, with less UI research and even where frameworks are used they are often built with a somewhat mobile first approach.
If I visited a site dedicated to hamburgers today, I would not be surprised if the "Log Out" button was presented as an image of a hot dog. It would be a mystery to me what that hot dog did until I clicked on it.
Compare this to 90's UI, where it would pretty much be unheard of to do something like that. It would have been a joke, or a novelty. These days that sort of ambiguous interface isn't presented as a joke or a novelty - it's the real product.
They later gave this up and almost everything else in their very reasonable guidelines based on actual research when they switched to OS X in a hurry and multithreaded everything. The early Mail application was a disaster, for example. Generally, people started complaining a lot about the spinning beach ball of death.
In contrast, modern UX guidelines are mostly about web design, how to make web pages look fancy. They also recommend instant feedback, but many libraries and application designs don't really support it.
I see little reason why building a UI today cannot be a superset of what was solved in the 90s so I’m curious to know what that solved subset looks like to you