Take for example the 'how do I centre a div' type of question. You will get to find an answer with thousands of up-votes that will be some horrendous margin hack type of thing where you set the width of the content and have some counter intuitive CSS.
In 2019 (or even 2017) the answer isn't the same, you do 'display: grid' and use justify/align: center depending on axis. The code makes sense it is not a hack.
Actually you also get rid of the div as the wrapper is not needed if using CSS grid.
Now, if you try to put that as an updated answer you find there are already 95 wrong answers there for 'how do I center a div' and that the question is 'protected' so you need some decent XP to be able to add an answer anyway.
The out-dated answer meanwhile continues to get more up-votes so anyone new to HTML and wanting to perform the simple task of centering their content just learns how to do it wrongly. And it is then hard for them to unlearn the hack to learn the easy, elegant modern way that works in all browsers.
Note that the top answer will have had many moderated edits and there is nothing to indicate that it is wrong.
SO used to be amazing, the greatest website ever. But the more you learn about a topic the more you realise that there is some cargo cult copying and pasting going on that is stopping people actually thinking.
With 'good enough' search results and 'good enough' content most people are okay - the example I cite will work - but we are sort of stuck.
I liken Google search results to a Blockbuster store of old. Sure there are hundreds of videos to choose from but it is an illusion of choice. There is a universe of stuff out there - including the really good stuff - that isn't on the shelves that month.
Google are not really that good. They might have clever AI projects and many wonderful things but they have lost the ball and are not really the true trustees of an accessible web.