A lot of the smaller drupal modules are unmaintained, buggy, or just plain don't work. Drupal advocates like to brag about the thousands of developers and modules in the ecosystem, but the truth is only the core modules and the most widely used contributed modules are production-worthy.

That, and even core-ish modules are maintained in a manner that's just plain unprofessional (I'm looking at you, Ubercart / Drupal Commerce): "Hey, there's a new version of Drupal Core! Let's drop development of (and support for) the current version of Ubercart that people are actually using and start writing a completely new cart system from scratch!"

it all depends. Example, if you want to assign a role to a new user when he signs up you can install http://drupal.org/project/autoassignrole module which does about 10 more things or just write one hook_user function.

If you install a module for every piece of functionality soon you'll end up with a huge codebase and the hell the author is describing.

You are responding to the author ;).

That said, I wholeheartedly agree.

Did Drupal dev for 2 years, and my biggest takeaway was: Don't go around installing custom modules for one dinky feature. Wrap it up in your own custom module.

Less dependency hell to deal with, and not only that, you'll have a much easier time debugging code you wrote yourself.