Outside is overrated.
I had a long thought about the topic of why people quit and tbh among everything else that's been said, what usually ends up killing a server PvP wise is lack of competition. If one guild is allowed to dominate forever and never lose, then frankly there's no fun in it. Content becomes stale for those not in the upper echelon and people get bored very quickly. Instances are a good distraction from all this if done correctly, but are not the cure.
I've been tinkering on a server of my own over time as a hobby, with no intention of ever getting it up, and I also wondered what it would take to get people to play, and stay, for a long time. It's extremely hard to retain users, and even more so to get NEW players. I mean christ, how do you advertise Mir as a game to a brand new player, and how the hell do you expect them to stick around when the game has no tutorials (something chronicles did right with its opening tutorial map/island) and the community is extremely cut-throat/toxic.
In the end I gave up because I couldn't figure it out, and life has a way of throwing wrenches at you to stop progress.
A few parting tips:
Avoid discord at all costs unless you enjoy losing braincells. Keep it to forums, where you have to type out your thoughts and read over them before finally submitting, and proper moderation can be done. Too often discord chat becomes a breeding ground of hatred and chinese-whispers that does nothing to help the server. All it takes is one person spewing utter garbage for it to be ran with and overnight you've got a problem that never existed that half the userbase is convinced is real. Besides, I personally feel like giving back to LOMCN and having your server discussion here promotes people to stick to a centralised hub rather than split off. The community is dying off, no need to help that process by moving away from LOMCN. Even if you think Tai is a grade A C*nt, swallow your pride.
If the community turns on the GameMaster, it's over. Be as professional as you can and sometimes that means ignoring people and not replying. Ironically, EuroMir and to some extent Chronicles probably did so well because the GM's were non existant in game, and to some degree even the forums. It was hard to even contact them, let alone get a response. If your community can have you reply at a whim, they will abuse that fact and take your attention away from the actual game. With that said - ignore players take on "balance". They are always bias. Always. I had a really neat idea about implementing a feature into a server where you can find and weed players who you can
actually trust to talk to you about balance. Feel free to PM me regarding this.
and lastly, enjoy doing what you do, and if you at any point stop enjoying it, take a break. I genuinely feel for this reason it's best to have a team of people running a server, rather than simply one person. Sometimes people need a break and others can pick up the slack. Finding people you can trust can be difficult but its not impossible.
As for the rest, well that's up to you. Creating an enjoyable server with the proper storyline, events, quests and engaging content is hard work. Good luck.