My theory is that two things changed: 1. complexity. As time goes by, systems become more complex, leaving less and less room for people to introduce changes sw

My theory is that two things changed: 1. complexity. As time goes by, systems become more complex, leaving less and less room for people to introduce changes swiftly. It's just like George Martin had a hard time shipping his latest A Song of Ice and Fire because there are just too many threads to figure out; 2. Culture. As times goes by, organizations bloat, and average quality of employees starts to decline. Plus, some people get promoted with controversy. Not everyone is Jeff Dean or Sanjay, after all. So, gradually and then suddenly, people create projects for promotion, and long-term vision goes out of the window. The two factors combined, a company transitions from being great to be mediocre.