I was a VB6 user back in the 90s, I think there's a bunch of reasons:

- Microsoft killed it: "let's rewrite the entire thing as VB.NET and make it completely different"

- The UIs designed in the RAD weren't particularly responsive in the sense of "responsive design" - generally you couldn't resize a window and have all the elements resize correctly. When I learned Java Swing and elements were defined programmatically as percentages of their container that was kind of eye opening to me.

- The small-time apps that were being developed with VB6 in the 90s are basically all web apps now.