Just play the OP heroes, that's what i told everyone when they asked me for advice on how to raise their mmr. Do not rush to learn everything, learn to walk before you can run. Do not worry about your limited hero pool, because my logic is, every year we have 2 cycle of balance patch. Even if you only concentrate on mastering 10 heroes every patch cycle, by your 3rd year you will have 60 heroes in your pool.

To be honest there's not much different between a well fed 4k,5k, and 6k carry on how they execute their skills. 90% of the difference that make a player 4k or 6k are abstract and intangible to unskilled players eyes. For example, a 6k carry know to handle the dual lane opponent and do not get easily demoralized when he is abandoned by his supports. That is because he understands the dynamics of Dota and the trade-off achieved when things like that happened. He know what needs to be done.

A 6k tinker wont cry when he gets 4-man ganked continuously from the beginning. He will try his best to limit the casualty done by his opponents, because he already know he basically won his team the game by simply being a retard magnet. A 4k carry will cry on the spot about how useless their teammates are, because he thinks the game is lost. Likewise for supports. How do i spot a 4k support? When they say something like this, "Oh shit, i'm supporting noob carry again." you know you've spotted a 4k support.

So how do you learn too see those intangible stuff that good players see? No, not from reading guides, but by having extreme patience. For me that is the true mark of mental strength and when you have this trait, you'll be able to see things to the end. You will see things that most angry players fail to see. If some of you didn't realize this before, Dota is a game of odds, because sometimes no matter how good you play, no matter how much you try to carry your team, you will still get crushed. High mmr players do not win every game, but they try to increase their odds of winning by trying to be a better player. Even the smallest thing counts when you want to increase your odds in winning. Even 3% increase in your winning chance from a 50% winrate is huge, because that means in 100 games you will earn 150mmr.

Edit:

A cliche quote for all aspiring lowyat.net dota players,

“We learn from failure, not from success!”
― Bram Stoker, Dracula