Not compatible with Visual Basic, including trivial incompatibilities that are immediately inconvenient (like different choice of file extensions).
But most important, as somebody who did a bunch of VB6 long ago: VB was marketed as "glue" for components that did lots of fancy stuff. Damn near everything in VB used a bunch of external components. CCRP project common controls, database interfaces, random junk that came with Microsoft Office like the Office menu controls, the Internet Explorer engine, Crystal Reports, you name it.
VB had the ability to use random OCX files that were on the developer's system for completely unknown reasons. You installed some random tool, and just got the corresponding OCX in the VB UI, and if you weren't too concerned about copyright issues you could just use it like that and package it into the installer. You didn't need any sort of development package, an OCX was usable on its own.
Reproducing all of this on Linux would have been impossible.
If you were a fan of VB you had no reason not to do it on Windows, and pirating Windows and VB wasn't hard back in the day.
The amount of people who wanted to write VB on Linux without any of what made it an useful tool on Windows would be tiny.
Mac has had similar kind of history in 3rd party libraries, and do iOS and Android to smaller extent, not as OCX/COM/.NET on Windows though.
Ironically GNU/Linux could have pulled something like this when D-Bus became a thing after KDE and GNOME IPC stacks gave birth to it, but impossible given the fragmentation that plagues it to this day.
I recently used it for a quick and dirty GUI application.
I sure don't miss Visual Basic, but Gambas is still great for producing applications. I would've preferred a "build me a statically linked executable" button, though; distributing Gambas applications isn't as easy as I would've liked.
That might be something for a rainy day. If I recall correctly, Fort has probably been my "worst" (i.e., the most useless) language learning experience thus far.
Gambas Basic – A Linux Basic Flavor in the Spirit of VB - https://news.ycombinator.com/item?id=37481718 - Sept 2023 (1 comment)
Gambas Almost Means BASIC - https://news.ycombinator.com/item?id=35361192 - March 2023 (47 comments)
Gambas: Visual Basic on Linux - https://news.ycombinator.com/item?id=22574385 - March 2020 (82 comments)