Same thing. L2 doesn't have a large enough dedicated audience to keep the forum active. Unless you come up with an idea that's not overused, nothing's gonna change. Basically, mxc cannot be revived, because its history is bound to L2. If it ever comes back it's gonna be something completely different.
This can work if you're interested in investing in advertisment of different kinds.
For example, one simple thing you can do is organize a big Hearthstone tournament. Or even weekly/monthly ones with smaller prize pools to show that you're actively interested in that scene.
If you can't invest, Twitch will not work. All of the popular games have huge established communities. Why would anyone bother with "another one" if there is nothing special about it?
You need to go much deeper if you seek cost efficient opportunities. Check what games are about to be released. Show early interest and try to attract that particular audience first. Encourage them to stay by motivating people to continuously post new content, actively question their interests, pay attention to rising forums of the same kind and quickly apply proper changes/upgrades in order to avoid damage etc.
A big ammount of similar communities start really early, like during the Alpha phase or even before.