https://www.theatlantic.com/ideas/archive/2024/01/boeing-737... - Gift Link: https://www.theatlantic.com/ideas/archive/2024/01/boeing-737... (good for 14 days from today)
https://qz.com/1776080/how-the-mcdonnell-douglas-boeing-merg... - 2020 article on the topic
I'm trying to find an article from circa 2007 on the changes at Boeing but I can't find it right now. Read those two and follow their various links and you'll get more information.
The long story short version is that post McDonnell Douglas merger, Boeing's management culture was replaced with MD's management culture and things have only declined since.