Is he ranting that Adobe Animate doesn't exist? Because it does and seamlessly exports HTML. I'm pretty sure if they aren't already you could get a bundler configuration for webpack that would build a single file data uris and all.
Jus as an example, Flash is able to redraw only whats needed on the screen whereas Canvas doesn't do this and works like a game where it blows away the whole screen every frame (assuming you're calling clearRect), hence why its best practice to use multiple Canvas elements, off-screen Canvas elements, etc but again, Animate doesn't do that work for you.
And up until the EOL of IE11 next summer you have to manually alter the output to make use of blend modes, which people use a lot of in Flash, if you want full browser support, which is pertinent in domains like healthcare.