They can be problematic, but for many they are just a convenient excuse to spend time with friends in a voice chat. It's not really more or less of a time waster than most other group activities.
Now playing alone for the dopamine rush of successfully grinding repetitive tasks: yeah, that's a bit of a time waster. Maybe therapeutic for some, and definitely not the most harmful way to spend time and get validation, but also a bit pointless. But I would argue that if you play an MMORPG alone you're doing it wrong. If you don't have friends at least get engaged in a guild and spend countless hours improving real-life social and leadership skills.
Another idea is this facilitates (re)creating these kinds of worlds and moments. Imagine your favorite MMORPG at your favorite time and imagine being able to recreate what feels like that time and place with other “players” being agents behaving in manners consistent in that context. Invite some friends. Have a good time. Throw it away.
That isn't very easy to realize though, not too long ago game designers thought that multiplayer was mostly about having other players as fun challenges to overcome. But people like having other people even if they never really interact, just having others there that you can show what you did to and talk about stuff is fun.
But point is, that realization isn't that simple, it took a long time for cooperative games to become common. In early days game consoles had cooperative split screen to let two players play at the same time, not because that was more fun, so it took a really long time for cooperative modes to become standard in online gaming because it wasn't at all obvious that people liked cooperative play.
MMORPGs were the main cooperative online games for a long time. Today we have dedicated short session cooperative games, those are still very popular.
Instead of feeling superior in a drive-by snark, explain to me why gaming for 3 hours after work while voice chatting with 3 friends is not a waste of time but if you do it on your own it is?
I'll bite. First, each human is kind of a separate universe, another 80 billion neurons to converse with, each with our own histories and vastly different knowledge and experience. In a conversation, we learn a lot from each other, and better understand how we can be different in skills, and even in basic things like emotion, motivation, etc.., better understanding what it means to be a human, and better understanding what it means to be in general. Also, it's very important for us to maintain some kind of social contact (I think written counts as well), because our brains language ability will degrade and we will lose critical skills including reading social cues.
Speaking of social cues, interacting with others specially in a complex environment where there can be severe competition as well as cooperation and difficult coordination, is something that also is worth practicing.
I have nothing against solo games, but this kind of thing is not practiced in a solo game.
Finally, I think other kinds of games (e.g. in competitive games) tend to have very simple interactions and objectives, compared to an MMO: there's a clear objective to win that's shared by everyone. Some MMOs have much more interesting interactions, where each person is interested in a different thing, and I think this contributes to a very rich atmosphere that isn't just 'Go win, try to win match, go out', i.e. more life-analogue (without other limitations of life, like you can't actually die, and being poor isn't as terrible as it often is IRL :( ).
So just be more in the real world? (I mean, IRL) Well, yes, but there are advantages to virtual worlds, as long as they're not designed to be simply addictive time sinks. And there are advantages to the real world.
The inputs to a computer game are more limited, you can't see people, their faces (and sometimes voices), the graphics are still a far cry from the more beautiful places.
Also, real life is full of responsibilities and large parts of it still, well, suck (bad jobs, exploitative practices, etc.). I think we're improving somewhat (greatly hampered by greed and power games).
If you have interesting activities IRL, like a great fulfilling job and hobbies (that are also potentially useful in other ways, like charity work), then by all means, but I think virtual worlds have their place in our lives.
3 hours of gaming alone can be valuable relaxation and entertainment but doing it while voice chatting can be both as well as social engagement. Just because one is more valuable from most perspectives doesn't mean one is a waste and one isn't. You don't need to be in a lobby with friends to enjoy or be good at CS:GO or R6, but I think it makes you more likely to become a better player and cooperate with your teammates if you do, and I think engaging in cooperation in one realm of your life can lead to easier cooperation in other areas. They are both wastes of time from the perspective that you could be building something or doing a creative hobby with an actual output, and they're both effective uses of time from the perspective that recreation and skill are important even if they aren't essential skills. In the end, I think playing MMOs without engaging in the social aspect is a waste and you might as well be playing Cookie Clicker, but that doesn't mean I think MMOs or Cookie Clicker are waste of time in and of themselves.
Now playing alone for the dopamine rush of successfully grinding repetitive tasks: yeah, that's a bit of a time waster. Maybe therapeutic for some, and definitely not the most harmful way to spend time and get validation, but also a bit pointless. But I would argue that if you play an MMORPG alone you're doing it wrong. If you don't have friends at least get engaged in a guild and spend countless hours improving real-life social and leadership skills.