While i don't often use debuggers, i find your argumentation to be false, at least for me, for one very simple reason :
A debugger can be a very fine tool for understanding how code you don't know works. Sometimes better than just reading it. Always better than litering the code with print statements.
I don't mean to imply that a debugger is not an invaluable tool. But it's just one tool of many, and it's an addictive one.
I once had to work for a few years with a development environment that didn't have a debugger. At first, this seemed like it would be impossible.
But I learned ways to work without one, and now I find that I prefer them. Only rarely do I actually require a debugger. I do still pull a debugger out occasionally for particular needs, but by and large I find that I work faster with simpler tools -- or by just stopping to think for a moment before I reach for the keyboard.
A debugger can be a very fine tool for understanding how code you don't know works. Sometimes better than just reading it. Always better than litering the code with print statements.