Tiago Ameller PRO said over 2 years ago on Hotwire Turbo Replacing Rails UJS :
I've devoted countless hours to understand Webpacker and migrate most of my projects. 
Now, I'm comfortable with it. 
But, when need to change something (maybe 10 minutes of work in the backend-ruby part) in a project not touched in months, there is a lot of problems in the "yarn part": Lots of deprecation complaints, need to investigate which part is failing ... one or two hours later, project is working again.
When looking to rails 4 happy times with Coffeescript and sprockets where asset pipeline just worked ... I'm not sure if we have better or worst framework nowadays.