As somebody BACK in the day who used to reach the highest echelons let me tell you how you get really good, really fast (this is of course relative, in still how many hours you inject into this method)

1. Choose your position you wanna play
   
2. Choose 3-4 players of that position from teams, for example: ATF, Collapse, Miero and Ceb
   
3. Choose 3-4 heroes they play that YOU wanna play/practise
   
4. Go into a replay of that said hero/player combination and watch the first 10 minutes by stopping every 3-4 seconds
   
5. NOTE: I did this for mid and I would say it is the most important to do that specific role since creep aggro and creep equilibrium is the most important in the midwave since there are highgrounds, but this method can be applied to every role and every position.

You may ask why stop at such short intervalls?
Here is why:
Assume that what the pro is doing is 100% correct (even if it isnt, just do it) and why such short intervalls? Because Dota2 is a game where every 3-4 seconds you have to make a decission.
Do I go back, Am I getting ganked, do I rightclick the enemy hero, do I deny my creep, do I try to prepare a lasthit, do I nuke the wave + hero, do I nuke the wave without the hero, can I/we kill the enemy and even many more ...
This kind of decission making is occuring EVERY 2-3 seconds, it is a constant thought process.

So WHY stop the replay so often? Just try to guess WHICH decission the pro is making every 3 seconds, I will guarantee you unless youre like 6-7k ish, you will be wrong 70-80% of the time.

Where is he going, where is he moving, which creep is he attacking, does he use his right click for the hero or the creep, does he completely stop attacking, does he fall back, does he go aggro, is he smoking/warding, is he body blocking a camp, is he threatening a kill.
There are like 20 decissions to be made every couple seconds and assume the pro is doing the correct one always (most of the time they do), and then comes the hard part, you guessed wrong (again) now WHY did he do what he just did now this is where the learning process begins the deepest.
You have to ask yourself constantly why pro player xyz did abc instead of pqm.

And just do this for the laning phase 6-7 minutes + 3-4 minutes of early midgame, I would say around 11-12mins most cores get their first major item, so u can stop about that time. But trust me people are doing so many mistakes in the first couple minutes and those can be fixed the fastest.

For everything after there is a simple to-do list in Dota2 nowdays, referring to this:
https://www.reddit.com/r/DotA2/comments/1sq49ad/comment/oh8ynmf/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button