Why does it have to be web-based? Discoverability? There's Minecraft and Lego. I discovered the CLI of MSDOS when I was a kid. It was a world to explore for sure.

There used to be pictionary online, web-based, which used Shockwave. iSketch I think it was called. There's probably alternatives these days, but I wouldn't know them. And regarding the Roblox issue: yes, some **heads were drawing ** pictures. Screw those people. This is what you get when you interact with total strangers. It brings the worst in people. How to solve that? Play with strangers-lite. Play games with people who are local to you. Yes, issues may ensue, but at the very least you can contact each other as parents.