Personally, I disagree. To be blunt, I see such analysis as being a waste of time.
Even if we were to invest the time required to pull data, separate it in whatever categories and this and that, we would still have no way to contextualize them. All we would have is a timeline, but that says nothing about the reasons people stopped playing, just when. The same way there might be people who left after the introduction of the Boogiemanglaives for reasons unrelated to that at all (which would be "accounted" for as "leaving because of it" by people), there might be people who left before that happened but still because of them, quitting when they heard it was going to happen (and those wouldn't be in the "omgomgomg Bogglaives" slice).
On top of that, whatever such analysis would have as a result wouldn't cause a population increase. There aren't droves of people at the gates just waiting to be told "people didn't leave because of X, they left because of Y." Without any actual positive result, it again strikes me as a waste of time and other resources for the sake of empty numbers that wouldn't bring any change.
Lastly, no matter what numbers we were to bring, history tells that the people who refuse to believe their personal narrative is correct wouldn't be dissuaded otherwise. We would get accused of faking/masking/tweaking the numbers, because they "personally know thirty-seven million people who quit because of <insert personal reason>." If you think I'm wrong, just take into consideration that to this day people come accuse us of faking populations, despite members of the community themselves debunking them.
Therefore, in my opinion, at best we would get numbers that people would go "oh I see" and everything continues the same; at worst we would get people arguing, saying that we didn't take into consideration this and that, or outright calling us liars over the data not matching their own reasons. One way or another the population - which to me is the only thing of concern here - wouldn't change because of such data. Still, if you continue to believe it's important, you can feel free to send a PM to someone like Proterean, encouraging it personally.