I think you missed the point of the new Fetch API. As JS is moving into a desktop and full application grade programming language, it is important to understand that not all the APIs are going to be easy and clean like jQuery has done for us. Your argument of having to add explicit code to catch the 404 errors is really indicating that you don’t understand what the API does. At the core level of the API is the ability to retireve a URL. It’s on you the developer to write code to handle the response.
Because JS has moved out of the webpage scripting domain, JS developers need to start thinking about more than just the browser window and begin to consider JS as a mature language with powerful APIs.
Furthermore, you willingness to include a large scale library rather than write a few extra lines of code because you think your code becomes cluttered is further propagating the “dependency hell” problem that is adding to the JS fatigue pandemic.