There are actually a number of tools that allow easy HTML5 authorship for non-technical users. We make one too - Construct 3 [1].
I think one reason Flash had such prominence was their effective monopoly. Remember when you had to install a browser plugin to get Flash? They reached ubiquity, but it was basically an impossible job for anyone else to achieve. So if you wanted Flash-like content, Flash was your only real option.
Since HTML5 is based on open technologies, there are lots of competing tools on the market doing exactly what some people apparently lament are no longer available. They're out there if you look, and arguably it's a healthier marketplace since there's real competition - although the choice is more complicated now, since there isn't that one option everyone uses.