It's not performant enough for what we want to do, and the constellation of "standards" around it are ill-fitting, awkward, and difficult to use.
We need a binary format special purposed for the task. Not CSS and literal XML and Javascript.
None of this is accessible to the animator. Some programmer bro can pick it up, but nothing has ever been as simple and as easy to use as Flash.
Why is it "not performant"? It is basically a set of bezier curves, just like other vector standards.
What is really bad that it is based on W3C technologies and requires a browser to display.