If you make a living selling bikes, and I make an exact copy of your bike WITHOUT taking the one you have just made, am I still stealing from you?
POTENTIAL revenue.
You're working from the assumption that all pirates would purchase desired content if it weren't made available for free (illegally).
The alternative you're ignoring is that a pirate can, and often does, choose different content to consume when initially-sought content isn't available to download.
You talk as if "POTENTIAL revenue" is equal to zero, but if you studied economics you would realize that there is such a thing called opportunity cost. It doesn't matter if it's just "potential" revenue, what you are essentially stealing is someone else's opportunity cost.
This is a different story if this person created music and gave it away for free intentionally (because he/she doesn't care, or in an effort to get more audience to monetize in other ways), but if Alice is providing X in exchange for Y, and you take X without giving Alice Y, then it is stealing. Your logic is "I wouldn't have consumed X in the first place if it was not free", and you are right. But at the same time, that does not change the fact that what you did there at the end of the day, no matter how NOT-valuable you see the product, is stealing.
For example, this is like drinking a lemonade from a kid's lemonade stand without paying the $1 price, and saying "You know what, you should be thankful that I even consumed what you created. I would have never drank this worthless beverage for $1, therefore what I just did is not stealing"