My own experience with my son is that he spends an enormous amount of time online on Pokemon. I'm still figuring out what the hell he's doing there. Some of it seems useful. He just recently got excited about JavaScript, to help his buddy run a server, but fizzled out after five hours. He just doesn't have the follow-through skills. I'm trying to gently help him forward with it, but there is an engagement problem. (And some other problems, we're paying a lot of attention to him right now.)
He's been through Minecraft, done some stuff, and then fell off when it got harder than he liked. Likewise with other video games. He loved Kerbal for 45 minutes and was done. He gets hooked on video games because they are shiny, and sniffs at some of the possibilities, but then drops out. They provide enough stimulation to distract him from whatever is bothering him, and to keep him from getting so bored that he might actually read a book. But they don't provide any steps up to an actual learning threshold.
Yes, some people can learn enormous amounts from video games and such. But I worry that those people have a particular set of focus and problem-solving and follow-through skills. I don't see much in the online environment to help identify and fill those gaps for other people. Ideally schools should be able to do that, and no, too often they don't. But at least they have the opportunity to put great teachers in position to do just that.
I definitely get the possibilities of video games and I hope I'm not hung up on conventional learnings. But I fear that for a large category of kids, these games are really net negatives. I'm definitely worried about my son.