VST as a format is platform dependent AFAIK. I think you can do something with WINE but other than that the authors of Ardour can't magically remake proprietary Windows VSTs in a compatible format.
As for your third point, I think Linux is improving in this area all the time. Ten years ago it was a black art. There's a lot you can do to set it up, but also a million different things that can be wrong and cause problems, so unfortunately you have to troubleshoot a specific setup.
VST as a format is platform dependent AFAIK. I think you can do something with WINE but other than that the authors of Ardour can't magically remake proprietary Windows VSTs in a compatible format.
As for your third point, I think Linux is improving in this area all the time. Ten years ago it was a black art. There's a lot you can do to set it up, but also a million different things that can be wrong and cause problems, so unfortunately you have to troubleshoot a specific setup.