Neither engine had great support for web, they aren’t designed for it and they both were trying to adapt a something much more complex than what HTML5 can handle. I guess Epic just gave up because it wasn’t working well with the engine. But I can say since the web support for Unity is pretty poor and it doesn’t run properly on mobile it’s not a great solution for it either.
For work we switched to something else that was specifically designed for WebGL and has full mobile and desktop support. It’s not as flashy but at least it works.