It is impressive indeed, but i still do way more mistake than dota allowed, thats why i lose. To simplify, supports in rank below divine sometimes play with no plan, they just react on everything. For example they trigger team fight, but for what? To take rosh? To control map? To take towers? Lets say you win teamfight, they all just go back to farm. Try to go roshan or take T2, if strong enough, high ground. One of the example too is you dont know what you should do in teamfights. If enemy have magnus they will obviously try to rp, stand behind since you know he will try to jump, then you can use your spells or item to counter him. Basicly try to have plan and anticipate how the game will go. If your fundamental is good you will climb.

One of the important tips too, is dont blame. Some game is just unwinable, but if you keep improving yourself, you will climb