I learned to program, even in assembly, before quality debugging tools were available (or I knew about their existence), so very much relied on "debug manually

I learned to program, even in assembly, before quality debugging tools were available (or I knew about their existence), so very much relied on "debug manually using log output". But once proper debuggers were a thing and I learned how to use them I never looked back. In fact I often use debuggers to step through new (or new-to-me) code even if it does appear to be producing the right output as I've seen too many times there are bits of unexpected behaviour along the way that are virtually guaranteed to cause a problem at some point (including cases where errors were occurring but being swallowed/ignored).