Eh, AFAIK Flash's big problem is the implementation - it's horribly inefficient and insecure etc, but in theory someone could make their own clone of Flash and make a much better version that works well for all that stuff.
Just have to say Flash and its an automatic down vote.
As some background, I used to program 3D engines in C++ for 20 years. So I know a little about the subject, and I hated flash back then too, but just out of ignorance.
first point - insecure
Would you rather have a safe that thousands of thieves try to break on a daily basis, or would you prefer that only casual thieves try to break it every once in a while?
I would trust my money to the safe that has been thoroughly tested. Checking for safety is pretty much all the flash team does these days.
inefficient
Its actually as or more efficient than JavaScript. Where there lots of crap flash ads and programs? Sure, but that is because Adobe made it easy to create flash apps.
I am writing a 3D engine in Flash that displays and updates millions of polygons at 60 frames per second. I can't do that in JavaScript yet.