You should have simply stated this in OP, so that we can know the actual reason why you created this post. Let me try to analyse or answer you.
Let me share my own ideas. It started after the merit system came. Frankly, I left it at that time. This platform never made an effort to attract new users.
According to you, the decline started when the merit system was introduced. Those who could not earn merits, just like you had to leave, hence the decline.
Those who roamed the forum like watchmen started to do more harm than good.
I believe that you meant the DT members. Do you mean that the activities of the DT members declined the forum traffic?
Too many platforms were formed and Bitcointalk system administrators started to deal with users instead of improving themselves.
It is natural that when there are alternatives, people shift to the alternative. For admins dealing with users instead of improving themselves, I can agree with you because more than $1M was invested in epochtalk but it didn't happen.
I wouldn't be upset if they banned me from this site right now. Because this place doesn't add anything to people anymore. And the so-called administrators of this place are still trying to protect its antique values.
No one will ban you for saying your view. You said here doesn't add anything to people, but it added to me.