Is DOTA still in your game list?
Never was nor will be.
I'm LOL audience, but it's not the game itself - toxic community is what I adore.
EDIT - hit post and left because distractions like…
Rarely spending time with family - is that a bad thing? I don't think so. Not all families are "interesting".
The bad thing is spending time with invisible people, socializing online instead of being with real living people, family or not.
I have two friends still addicted to WoW. One is doomed, noone sees him any more as is always home doing whatnot raids. Perhaps I should say "had" a friend.
Another one is different and comes often for a coffee or gets drunk with us so it's IMO still okay. I'd like him more if he was into singleplayers, but well, whatever makes him happy as long as he's not ruining his life.
If you don't have what your brother wants, sorry man, but you can't help his MMO addiction. What does he want anyway? What's exactly that something reality can't give to him so he has to escape into virtual world? Do you know? I suppose you don't.
30 you say? Go to him when he's in dota match with tons of beer, pretend you're interested in what's going on the screen and get him dead drunk. That's how you'll find out.
You might pull out an excuse that you don't drink, but man, alcohol is something humanity and civilization evolved around. Find one of his ex friends who do drink to do the "dirty" job.
A couple of notes more.
You're new so perhaps you didn't expect a suggestion like this one above. Sorry, but I tend to be blunt.
I can't recommend pot in this case as it won't solve anything, in fact it could get things even worse if he notices his DOTA performance improved while stoned. Being drunk however will kill his reflexes.
Keep in mind it could have been worse than it is - at least he's not addicted to lootboxes.