I've had difficulty putting it into words myself, but this sounds like my experience with sub throughout the last few years and the reason I don't like being on it. I can especially relate to the loss in sense of humor. That is one specific thing I always notice that happens when I get off opiates, is that once I'm through the WDs and stuff, I laugh sooo much easier and at way more things. I'm a lot more serious on suboxone.
I posted this on another thread not too long ago, but I felt like suboxone took away a percentage of my personality. Not something significant, but it took away that 'spark' I'd have and kind of just made me bland. Sort of like I was still me, but it took away 10% of my personality which just made me....well pretty boring.
I don't really get overly excited or saddened on it, just pass through life. Completely lose my drive to move forward or have any sort of change. I specifically remember last summer when I was kayaking on a gorgeous day with my at the time girlfriend, and I can remember feeling like this SHOULD bring me some happiness, but I was just there, and not experiencing the moment like I should have been. I just was NOT deriving any joy out of what should be a fun time. I had been kayaking before, so this was not just the result of disliking what I was doing.
I don't really have any helpful advice to you. I feel that way on suboxone, but it's fucking hard as hell for me to get clean off of everything and I don't feel interested in anything when I'm WDing, so I'm sort of trapped in my mind and body knowing that I'm dulling out my life.

It's not a fulfilling way to live.