What if Counterwatch doesn't improve my skill?

Counterwatch is not a skill upgrade. It is information, and information only helps if you act on it.

What it can genuinely do is narrow the gap between a decision and the feedback on it. You see the matchup before you lock a hero, you see which of your heroes actually performs on this map, and after the session you see whether the picks you made were the ones winning you matches. That shortens the loop that improvement runs on.

What it cannot do is aim for you, hold an angle for you, or make the call to swap when you have decided you are going to make this hero work.

If the numbers are not moving, the useful move is to look at a losing session in the match history and ask what the data is telling you that you ignored at the time. That is usually a more productive question than the win rate itself.

And if you just want to be told it is not your fault: it was the tank's fault. Enjoy your next match.