IMO This is why Unreal (and Unity) for web is just not a good fit. Most games made in those engines use 100s of megs of assets. You download the 100-500meg file, to your hard drive, then run the game. That's not the web.
To be good on the web requires designing your game to start immediately with the minimal amount of downloaded. Maybe stream some stuff in the background but be playable immediately. AFAICT neither Unreal nor Unity do that by default. You can maybe coerce them to do it but most devs don't. As such they get these bad experiences when they try to put their creation on the web
Sorry to hear that! I will say that usually if you wait long enough, it will eventually load. Try popping open your dev console sidebar, you should see assets downloading over the network.
If it does crash, you'll be able to see why. I'd be interested in seeing any bug reports if you do fine some, we're always squashing bugs over here!
