Your question is interesting: “Did Bernard Shaw thoroughly investigate what the bible said or were his thoughts and observations based on how people practiced their beliefs?”
I have thoroughly investigated what the Bible says, and have found that most of the things it says poorly depicts God, and thus dishonors Him (which is more than what Bernard Shaw feels). Bible is a simple book of just 31,102 verses, and you have 86400 seconds in a day—imagine how many times you can read the Bible in a year!
What claims to be written about God in the Bible does not match with what God has actually done in the nature. His style is so majestic that He cares for more than what is just required. Look at one of His acts—our planet home. It is more wonderful than it is convenient, more beautiful than it is useful. God could provide only what removes our hunger and thirst—yet look at the variety of each fruit, flower ….
Now in the backdrop of this, you read Exodus. The way many times Israelites had to quarrel for their basic needs such as food and water shows that God was not leading them. (Exodus 17:2) If He was really leading them, He would have taken care of it more than just sustenance even without anyone asking for them (Mathew 6:8) At one point they were even about to stone Moses (Ex 17:4)
If God would not lead people the way it is depicted in exodus then it means accounts are just human thoughts. This is true of most of other accounts in the Bible--something true prophets like Jeremiah could insightfully declare. (Jeremiah 8:8)