I agree, the gui may look old, but since the laws of physics haven't changed since Spice was developed....
I did not talk about the GUI. Its perfectly fine, to have an ugly GUI if it works. Rotating parts for example is not as intuitive, as i am used to. As said, it feels like 199x experience...
It doesn't. I don't think you get your references right.
While part of the GUI uses basic Windows GUI (menus, toolbars, dialogs), which is fine - unless you prefer this ugly toyish ribbon menu crap, which in itself is not even part of the Windows base controls, I think the problem you (and quite a few others) have is with the schematic editor, which implements a GUI that is not a "90s" GUI, but really more like a DOS-based UI, with heavy use of function keys, no sensible use of right click, the impossiblity of selecting objects just clicking on them, etc.
That part is not at all a "90s" GUI. GUIs of the 90s were perfectly capable of exposing anything we're used to today.
It's more that many CAD tools in general tend to suffer from the same thing, probably mostly because many of the most popular ones have had versions since DOS and have kept some of the UI for legacy reasons. I don't know the full history of LTSpice (just remember that it was initially called SwitcherCAD), but the author probably also had habits dating back to the very old days, and used to other CAD software.
Maybe just all a detail for you, but would explain james' reply.
Generally speaking, again many CAD tools, even recent versions, have weird quirks and UIs that are definitely not following the standard conventions of GUIs.
Regarding LTSpice in particular, a slight overhaul of the schematic editor and the waveform viewer would do the trick. It's not a huge endeavor.
But as with other CAD tools, I guess this has been put to low priority due to the fact that 1/ it's still usable and 2/ there are millions of users used to LTSpice's UI, and changing it would probably cause more friction than it would remove. And yes, that's the case with a lot of other software, and often explains an apparent lag in modernization. Just the way it is. It's very hard, if impossible, to please both your existing user base and new users.