Sorry, that's simply not true. The tech was ahead of its time. The implementation was intuitive. Only developers and Steve Jobs hated it, because Flash made it way too easy for anyone to make something fun.
Sometimes good products happen despite bad technical foundations.
Let me introduce you to itch.io[0] where, in fact, people bang out HTML5 games at a rate that will stagger your eyeballs.
(Even me, a resolute "backend-only" dinosaur managed to use a HTML5 game engine to knock something out playable in an hour or two.)
[0] https://itch.io/games/platform-web - ~689k results