Lots of people say performance was good, but that seems to be through the nostalgic lens of a handful of cool games.
Those did sometimes run really great, but most implementations were indeed very slow.
I remember vividly because it was part of my job back then to help with web performance and when we measured page speed and user interface responsiveness flash was almost always the worst.
I am not and have never compared them in the way you say I did. You literally wrote ”Or that it was worse than the performance of doing the same thing in modern HTML+CSS now.” so I had to somehow repsond to that strange claim.
Of course modern computers are orders of magnitude more powerful! But Flash was definitely generally worse compared on the same hardware and network stack compared to vanilla (non-plugin based) web tech.
Maybe at rendering menus and documents, but flash had graphic routines written in optimized assembly that simply weren't possible with JavaScript on that era of hardware.
I feel like people are talking past each other a bit here. FlashScript was never very fast, and rendering a document as a giant collection of bezier curves was not fast, but the people doing animations with it were getting the equivalent of modern day CSS3 animations + SVG, and it ran nicely on hardware two orders of magnitude slower than what we need for CSS3+SVG
Right. But that doesn't mean the performance of Flash was bad for what it was doing. Or that it was worse than the performance of doing the same thing in modern HTML+CSS now.