If code had instrumentation for every variable someone ever looked at with a debugger it would be unreadable because it'd be buried under instrumentation code, configuration to only enable instrumentation when needed, ... That's not to say instrumentation/logging/... aren't useful tools that can be more appropriate, but "never use a debugger" seems like a misguided dogma that seems surprisingly common. Part of the strength of a debugger is being able to look at all the things to find the ones worth a closer look, without having to add instrumentation or logging to every single one.

> by adding [...] comments, [...] etc

If you need a debugger, those are not there or not good enough, and you can only meaningfully add them after you understand what's happening.

(EDIT: there is also a wide variety in what people count as a "debugger" further muddying the debate)