Playing online changed who I am for the better. If I hadn't thrown myself off the deep end, and gotten so involved with video game communities that I'd end up leading them, I'd definitely be a different man. For better or for worse is another argument, but I will say that running communities has given me a lot of perspective, wisdom, knowledge, and experience I otherwise never would have been able to find elsewhere. If it weren't for this "waste of time", I wouldn't be here.
Here's two ways you can differentiate videogames from being a waste of time versus being a worthwhile pursuit.
1. Moderation is key. No, not moderation like, "____, please don't spam or else I'll report you for rule breaking." Moderation as in keeping everything in equal parts. Balance your videogame life with your real life, and never let one get neglected in favor of the other. You can have both, but it requires strict discipline which you must learn, or else you'll fall off the deep end.
2. Don't just play: get involved. Videogames are a consumable good, but they can be so much more than merely an entertaining diversion for a few hours. There are communities out there to interact with, and people to meet with similar interests as you. There are mods to be made to enhance players' experience, allowing you to build on a skills you otherwise may never have had a chance to use, all while existing within a medium you and others enjoy. And lastly, there are games to be made! Every game developer is/should be an avid gamer, and these people who bring joy and art to a large, willing audience must first find their beginnings inside of the world of videogames. But the point is that if you enjoy videogames, you should do more than just play them; you should be a content creator, not just a content consumer.
I've had a lot of time to think this topic over, and every now and then I start to doubt myself. But every time, I always come to the same conclusion: videogames are not a waste of time, so long as you don't treat them like one.