The link to twitter and Facebook are not visible enough. They are links in the middle of the game description.
Since people avoid reading as much as possible, most of the player will simply never see the link to twitter or Facebook.
People follow the game on Game Jolt more easily simply because the button is there at the top.
You also have to ask yourself why people will follow the game on twitter.
From your timeline it seems it will be mainly interested for people who are invested in your game and want to now when there is something new to it.
Realistically this is a pretty narrow audience. Doesn't mean this is not useful and important but it would explain the low engagement.
you had 2400 players only a fraction would read the description, only a fraction of them would click a Social Network link and only a fraction of them would be interested in the content you share there.
I think having a more personal voice is more appealing. So asking people to follow your own twitter account might be more attractive. People might be more interested into following the guy who did the game, what he is working on, like etc.. than an auto promotional account with just some updates. In short, on social media content is as important as in a game. people will follow good content.
But if you plan to have a kickstarter in the future maybe my website might be useful:
http://whenitsd.oneYou can create a page that people can subscribe to to get informed when (if) you launch your kickstarter campaign for the game
Since the purpose is clearer you might get more follower in this channel.