No, they can't be solved. Your comment suggests HTC has come magical way to code the game so everyone enjoys it.
This is not going to happen, people come and go. HTC designs the chess board, play the game. I left, got busy, life intruded, had to make a choice between playing and working. Almost 20 years of playing and this year, work intruded. My reasons, my business, not one single thing HTC can do to change that.
Play The Game. The game is what you make of it, nothing else. People sit in here and complain about so many things that are 100% absolutely their issues to solve but expect the coders to fix it. Not going to happen 
Every single person has their expectation of what the game "should" be and it is physically impossible for HTC to code it to fix it for everyone. People complain about the scoring, HTC fixes it, and those who were not complaining are now complaining about what was changed that they thought was fine. I'm not surprised HTC and company drink, I'm surprised at how LITTLE they drink!
You cannot code something to increase the fun for everyone because everyone has something uniquely different they think is fun.
They built a pretty nice game board. Go play the game. I'll be back later, when I can. Might even shake off the dust and CO an event but not right now. When I do it will be for my reasons, on my time, when I feel like it, regardless of the status of the new version, because the community around this game is as much, if not more than, the game itself.
But my original point stands, people leave for reasons, and there are as many reasons as there are people.
I would say any reason someone has for leaving is a valid reason.
My point is that some things can be adjusted. A few years back NOEs were rampant. It seemed like 8 out of 10 missions were NOE. Game play was basically "wack a mole" in jumping from base to base to defend. HTC adjusted the DAR and the number of NOE have decreased. The NOE wasn't REMOVED from the game but it was made a bit harder and so it wasn't the quickest easiest way to grab a base any more.
An adjustment made, and a larger portion of the subscribers are happy.
What if a way was made that the number of attacker inside a DAR circle adjusted the percentage of buildings that have to be dropped to make the town go to a white flag? If it was under 10, you needed 50% and for every player over 10 it adds another 5 buildings. The larger the "horde" attacking the more buildings you need for a white flag, but if you use a small force you need much less. Would you see the "hordes" split up and work 2 or 3 bases at once?
Could it be abused by some players to aggravate others by flying in the circle and not helping out? Sure about as much as a player popping DAR on an NOE mission. And the good thing about something like this is it isn't taking AWAY the horde mission. That is still there and in most cases they bring enough ord to flatten a whole town , FH, BH, VH, ammo, etc, etc. It does open up missions to small crews that would not like to fly in a horde as well as adding more places for defenders to find fights.
A change to code to enhance game play. Thats the kind of stuff Im talking about. Everyone has a valid reason for leaving, but again some of those reasons/issues could be solved. Heck if there was a pool of money we could donate to to augment subscriptions for those hitting hard times it would be another solution to a "reason" some people have to quit. Sure there are a number of reasons/issues that cant be "fixed", but is that a good reason to NOT look at the reason/issues people quit?
