- 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.
I know you asked for "the language", but Object Pascal really ain't that bad to get around. If you were proficient in VB6, you should be fine adapting. :-)
What changed was the level of popularity and acceptance of those tools.
I think it comes down to trends and programmers psychologically subconsciously not wanting to be mistaken for users.
Because unfortunately what subconsciously is accepted as programming must involve colorful cryptic text. And if you are just dragging things around and setting parameters, you are not doing that, and someone might accuse you of being a user.
Not saying it makes sense, but that seems to be the explanation.
But look at WordPress, VB.NET, n8n, LabView, Unreal Engine, Houdini, Unity, etc.
- VB apps weren't great from the point of view of internationalization, accessibility. Nor were they easy to adapt to multiple screen sizes. Hard to retrofit the ecosystem to make that right it seemed.
- Microsoft decided to solve that problem by attacking a different one (symptomatic of their internal politics), by pushing .Net. That smelled to me of the victors of an internal battle (VB vs .Net) taking over the real estate of the VB ecosystem. However, the developers of VB apps got a vote, and they bailed.
Microsoft's timing was also not great in that the web and mobile revolution arrived just as they were wrangling with all this and made a lot of the discussion irrelevant. No one starting a new app today is going to reach for VB.Net, they're going to default to a web app. If desktop perf is the target, they'll grit their teeth and try to figure out what desktop tookit (WinForms, XAML, MAUI etc) they should be using...yet more friction compared to webapps.
It's a tragedy that scratch-your-own-itch desktop apps went away, but I can't say I am at all surprised.