Discussions or complaints about how MB is dead have been going on practically since its beginning (if you do a search for "forum is dead",
the first threads start popping up in 2005).
Maybe there is an objective way to judge if the activity has gotten lower which would dispell any doubts, but frankly it doesn't matter. As many people point out, it is what you make of it.
Maybe some people expect more immediate interaction, or more detailed interaction or more interesting debates. Those same people should then definitely try and start some interesting discussions.
My approach to the forum at the moment is actually to avoid long and drawn out debates. It requires a hell of a lot of time and I guess I'd rather be doing something else than arguing over the internet. Them days are long past. If you have a job and a life, then your forum activity is definitely not gonna be very involved.
So in that sense, MB is actually perfect for me. It's not boring because within a span of 24h, normally there are at least one or two pages of threads with new posts in it. Anything more than that and it becomes cumbersome. So for me, the size and activity level is perfect.
It will be curious to see if this forum will ever truly die, apart from the owners pulling the plug. I'm a little fascinated that in this day and age there are still new people, some of which quite young, signing up because they wanna talk about music. It's pretty amazing. Let's see how it goes. It's clear that I, much like Exo, am here for the long haul.