If SE had launched the game with addon support, or had at least implemented it on schedule, this wouldn't be nearly as big of an issue. The fact that people had to turn to 3rd party programs just to find out if they were doing decent DPS or to help them react to a boss faster opened the floodgates. Once you're running a third-party program there's little barrier to simply tacking on another "feature" like this. A regulated addon environment could have enabled the "essentials" while leaving grey area stuff like this outside the scope. Far fewer people would be willing to install a third-party program if they could get those things through a first-party sanctioned channel.

I am not advocating for third-party programs, DPS meters, or anything else, but it's an unavoidable fact that a very significant portion of the playerbase wants certain things and will turn to a third party for them if they are unavailable, as they have in this game.