Ok, let me address those thoughts since some may be right some are plain wrong.
1) Too many bad updates? I basically didn't touch the game for months until recently. No updates. Zero. None. Since I moved to a different country and I was super busy. So I doubt it was due to too many updates. In fact it may be due to too FEW updates.
2) Fox hunting, riding ponies? Fox was there as an easter egg. Same thing that I have dropped for surprises on the game. Riding ponies? It was requested by some they wanted to ride a horse. In any case... it was added what? 3 years ago? Nothing recent.
3) Nothing to do with flying planes? Ok. Updates have been mostly adding new planes, improving features of the planes, armor, speed differences, etc... basically, almost all updates I make are for the planes with something else in between.
4) World chat being for subscribers only, the chat is what sucks people into the game: maybe, but world chat is for subscribers only after rank 15. That means you can literally spend weeks playing before you are out of world chat. I don't think that´s what sucks players in, otherwise, you would see tons of people in the world chat talking and then at rank 15 leaving the game.
5) You preferred when it was WW1 only. That was almost a decade ago now.
So while I get your frustration and what you like or don't like, it doesn't explain much for the general public recently.
Now, I'll give my view since I have data to base it on:
1) Old players leave because they are old players. Like every game, people get tired of them. I used to play WoW, I don't anymore. I used to play Final Fantasy. I don't anymore. Perfectly fine games, but you grow out of them. So old players move to different games or out of games, it's just the law of passage of time.
2) Some players, and here you are right, were ruining the game for everyone else. The problem is that those same players also spent a large amount of time here and had a large cult following. So banning them, would get many people mad. When I did that, many left. I had to make that choice. World chat may suck some people into the game. But getting killed as soon as you join for the first time 30 times in a roll, does not. And I can see it on the stats. Newbies were giving up super fast when they came across players that massacred them for points time after time. And they were not returning. What sucked people into the game was to have fun. Coming in and see you can kill a few people and get killed too.
3) Visibility. Several years ago, games in the app stores were visible due to quality and reviews. That meant, if your game was good and got nice reviews, it would be listed on top of the store for everyone to pick it up. It worked perfectly fine for me and for most developers that put time into making good games. Nowadays, apple and google, display the store content based on who pays the most for advertising. So someone with a crappy game but $200k to spend will be placed on the top spot for everyone to see and download the game. Meanwhile, the others, no matter how good the games are, will not be even visible. This can be easily proven by searching for "dogfight" or similar, which used to display this game first for obvious reasons. And sometimes you get all kinds of other names and have to scroll way down to find Dogfight. This has stopped DRAMATICALLY the recruit of new players since they simply don't find the game unless some existing player tells them. Now only whoever spends on Apple and Google ads, gets the players.
4) Massive amount of new games. And any game competes with the whole system. Games compete for time. If you are watching Netflix, you are not playing. If you are playing Fortnite, you are not playing Dogfight. It brings me back to point 3. I either spend a fortune on the store, or it's hard to get noticed.
5) Drama. There was a lot of drama in the game. In fact, there always is in every game with a community after several years. That's why many games decide not to have a forum or chat. To avoid drama.
Those are some of the things.
What I'm doing moving forward... fix some of this stuff. Basically focusing on getting newbies to join and free (world chat is free, almost everything is no subscription required until rank 10/15 already) and protecting them a bit against players who would bully them. That's the whole idea behind the new armor system.
I'm also working on new missions, and they take time since they require whole new systems to be designed and coded. For instance the new bombers mission is only half of it. I want people to be able to jump into different planes and play together in the same plane. Like 1 flying and another person on the same plane but on the gun. That's why I added those 2 bombers into the german side. And so on. But the complexity of those things require time and that's why sometimes you see a brain fart on my part and things look weird because I couldn't think of every possible escenario.
In any case, focusing right now:
1) Better level playing field for all ranks.
2) New missions and planes and vehicles.
3) New stuff in the terrain and air that belongs to the new missions.
4) More cooperation between missions.
5) System to allow for more variety of airplanes. So you would pick different planes and not only your best one depending on the scenario.
And hell yeah, I make mistakes all the time, but that's why I try to update with changes and fixes. I'm well aware that not every change people will like. So it's not an easy task and prone to mistakes.