I think a few comparable development tools have sprung up, including ours, Construct [1], which is very much web-first.
I think the reason people say nothing replaced Flash is because now there are lots of tools instead of just one, as anyone can target HTML5, so the market has fragmented; and the market has changed, as people develop for app stores and platforms like Steam, so the web isn't as big a focus as it used to be (although it's still important).
Construct is great. I used it to make a game with my daughter. The way it jumps straight to the fun bits and then gives opportunities to learn about programming concepts is great.
I couldn’t bring myself to pay the hefty monthly fee though, knowing my kid’s interest would wane and then her creation would be forever inaccessible unless I continued to pay.
One thing I would have gladly paid for is asset packs, being able to adapt some great sprites and background art would have been a killer feature.
Just to be clear, you can still access your projects without a subscription - it's only editing that a subscription unlocks. We also have a full asset store here: https://www.construct.net/en/game-assets
I think the reason people say nothing replaced Flash is because now there are lots of tools instead of just one, as anyone can target HTML5, so the market has fragmented; and the market has changed, as people develop for app stores and platforms like Steam, so the web isn't as big a focus as it used to be (although it's still important).
[1] https://www.construct.net