Right you are @tedsuo There are many ppl not writing tests and not using staging and best deployment practices. This is true in every CMS and WCF. I don't believe it it any more prevalent in Drupal than anywhere else. Drupal invites a lot of BEGINNER types to the arena of web solutions. As such you will certainly find the things you mention.
I don't agree with your suspicion that big shops are hacking core and building custom CMSs upon Drupal in a vain effort to try and gain source control features. Rather... I'm aware of big shops sticking to Drupal bets practices and using Features, Strongarm, Plumber and other modules to get configuration into code and keep it source controlled.
If Drupal deployment were the nightmare you s=describe, then the phenomenal adoption of Drupal that we see today would make no sense. Why would the Georgia Tech Authority decide to move SIXTY-FIVE sites off of a Oracle, Java, Vignette solution and onto Drupal? Well.. It is isn't because they like nightmares during deployment.
Drupal is growing up. The issues that plagued us 5 years ago when I got involved are being solved with varying degrees of success and effort. We're not where we want to be but the market is eating us up. We are bullish about our future and know that out continued improvement will only serve to better our position as the leader that we are in the web space.
Doug Vann [Drupal Trainer, Consultant, Developer] http://dougvann.com