I'm legitimately very confused as to where you get the 'information' that player retention is related to stacked matches. Yes, after the promotions end, the game loses concurrent logins. This is more likely due to the nature of people who purchase a game solely because it is on sale, or due to the recommendation of popular YouTubers. A few days/weeks after playing the game, an overwhelming majority of them will move on to whatever is on sale or recommended by popular YouTubers next. I see nothing to indicate this has to do with faults in the game or the actions of our community. This is the nature of the promotional channels that Guns of Icarus has been very successful in.
I feel as though you're accusing certain unnamed players, clans, groups or even play-styles of a negative impact on the game that simply isn't as definite as you believe. I would include myself in this group, as a member of a publicly competitive clan, and one that plays with it's own crews whenever possible. I could definitely be accused of "stacking". As such, I take the accusation that I am part of a cause of players leaving the game fairly seriously. Stating that some teams don't do it 'intentionally' doesn't negate the fact that you are still saying their actions are always detrimental. They aren't always. It can make some people upset, I'll agree. But to be completely honest, I probably get just as upset at team members who refuse to coordinate. It's just a matter of perspective.
I appreciate the time and effort you're putting into this. I really do. I just don't believe that any part of this community should be vilified as completely as you're suggesting. I feel as though you're trying to state your own personal opinion as a matter of fact. Does "stacking" happen? Yes. Does it make some people angry sometimes? Sure. That's about the only things that you can say for a fact. Anything else is conjecture. In my opinion, 'stacking' is not game breaking. In fact, you can dig up tons of posts on this topic, some very old, and yet the game is still running smoothly. In this game as a whole, we actually do a really great job of welcoming, training, and retaining new players.