I'm not a big fan of complicated GUIs or practically any GUIs to be honest. Their complexity is vast and code wise, they often make up a majority or at least very significant part of an application. I get it if you're selling a product, but if it's just an internal tool, I find it's usually just not worth it in the long run.
This is literally why VBA+excel are so pervasive: it’s a way to slap together a UI with no/minimal code.
There is a vision of a future where non-CS engineers could function with an interface that’s basically a Jupiter notebook with “import simulator” at the top, but managers are loathe to make that level of scripting competence a requirement for an already fairly specialized role.
Excel combined with APIs and either minimal VBA or COM AddIns is also perfect method to do random data entry or query interfaces for your end users if you have MS Office on Windows as your common office platform.
