I am not sure if I get your point then. I think it is important to see the patterns of bad decisions in the past to improve decision making in the future.
That those mistakes were not done deliberately and with good intentions is a completely different story and that in hindsight everything looks so clear is also well known ;-)
Why is HTTP/2 Server Push being rescinded?
Why do user agents not provide additional types for <script> based on runtime installations?
Why isn't there a renderer API that allows me to use painted trees in <canvas>, but there is a bluetooth API that no one uses?