“How good will I be at German if I watch YouTube for 2000 hours?”

“How good will I be at German if I watch YouTube for 2000 hours?
I’ve watched around 175 hours so far. I basically started from scratch. I would estimate that I’ve got thousands of words in my passive vocabulary so far. I’ve also mastered the subjective-object-verb order naturally through extensive exposure.”

Have you tried talking to a German person yet?

And do you speak out loud what you hear?

If you try talking to a German person or German speaker now, you will have an idea of where your German is in a practical sense. You will know some things you don’t understand and maybe learn about what you have trouble saying and communicating (maybe issues with pronunciation as well).

And you can try again after another 100 hours to gauge your progress.

If it works, cool.  But I wouldn’t say it’s guaranteed to be effective.

I would not blindly pursue the strategy if it’s not working though. You figure that out by testing it. And I think you should try speaking German to a German speaker.