Proboards type forums are also pretty much perfect. Section/Thread/Post, no further levels, full size posts with signatures, pagination for everything.
Excel has the distinction of being basically the only way a normal person might ever consider writing a program. In that, I consider it one of the coolest technologies out there. Not only that, but they had reactivity like what, 20 years before web dev commonly used it? In an alternate universe, somewhere millions of people are making programs with Excel 12.0, which lets you make pages that are actually Vue templates referencing your data.
Most editors have solved their editing domain pretty well. If you go back to 2000 or so, any most editor will be fine aside from lack of nondestructive stuff. They added over time but the core model is the same in new vs old Photoshop, gimp, DAWs, video editors, etc.
I like Android's UI, but lately touch devices have been getting so heavily gesture based and I constantly accidentally switch tabs or refresh pages.
The vast majority of UIs from 1990-2005 seem to have held up just fine. I think UIs that don't hold up are because they're trying to model something inherently hard and make it easy(Like anything 3D) or they're working with limited hardware and don't have full size screen and a mouse. Without a mouse you have to encode things in timing that would otherwise be encoded in the different button presses.
There's no separate hover and click, no right click, no middle click.
I wonder why there isn't more phones with touch sensors on the back that can actually as a mouse, or why GBoard doesn't have a laptop touchpad type interface for dealing with legacy non mobile sites.
The tabbed web browser hasn't changed fundamentally since forever. People keep trying out new ways of managing tons of tabs, but all the major browsers today look pretty similar to early releases of Opera.
Aside from the ribbon, Microsoft Office remains mostly unchanged in terms of basic interactions. Even keyboard shortcuts from 20 years ago continue to work the same way today. Remember that the Office ribbon came out in 2007, which makes it 16 years old now! You could say it has stood the test of time very well, too.
Desktop and mobile operating systems have figured out sets of basic interactions that work for them. It's been a while since a new iOS update changed the way I work with my iPhone. Likewise for Windows and macOS. Once you get used to them, they become invisible, humming along without drawing attention to themselves. In contrast, tablet/convertible UIs are constantly in flux, trying to figure out how to make all their diverse input methods (touch, stylus, mouse and keyboard) work together in harmony.
I'd say most software we use today is pretty damn good, and doesn't change all that much. That's why everyone gets mad when e.g Spotify decides to suddenly change how the UI works. People aren't used to their tools changing very much anymore.
Old reddit and HN are nice. Maybe I just strongly dislike avatars. It becomes about who said what instead of what was said.
Forums like SMF could work, but only if they're mobile friendly. Sorting by down/upvotes creates an unfriendly atmosphere.