Using the debugger to understand/read code is invaluable. Seeing live stacks is so powerful compared to static analysis.
I'm not convinced. At times it can be valueable, but at times you can go around in circles, changing checking variables/break points all the time, but never finding the problem. Often thinking about the problem and what is important is what you need. Playing in the debugger is fun and feels like progress, but it can just be a distraction from understanding the real problem.
I'm not completely against debuggers, but in my experience they only are useful either to get the trace of the problem when it first occurs and then use static analysis until you have a theory the debugger can prove/disprove - but only prove/disprove that theory don't keep looking: you will feel productive but in fact be spinning circles