The only game that I can think of is DartMUD. I really enjoy that game. Please note that i'm a newbie and I'm talking about everything from my point of view.
DartMUD is set up in a medieval timeframe and uses a feudal system.
There's plenty of magic to be learned/discovered. There are few mage guilds and a healer's guild. The spells definitely are not stock. My character is a newbie mage and so far I've been able to heal, call animal familiars, send messages. There's so many spells in the game. Some must be found through exploring and questing. Others, (mostly the low-level spells) are available in the mage guild's study rooms or by getting experienced mage's to write them into a spellbook for you to study.
DartMUD has a great economy. You can explore, quest, hunt, gather or crafting for items to sell. Everything in the game is player made and everything can be customized down the smallest detail. There are over 300 food items to make (that number was found in an OLD post, back in 2007).
I'm not familiar with this. But there is a Lord/Vassel system. Lords can appoint Knights and stuff. Guilds are player run and there's so much more. Commonfolk and gather support and rally against the current Lords and take their thrones.
Dartmud has permadeath, but I don't think its very common as long as player takes precaution. I'm not too familiar with this either, but you should have an amulet that traps your soul if you die. If you have that you can find another body. Even if you don't you can "tell" to another player who can rally help and resurrect you. But you'll pay with skills or coin.
There isn't an app process. But you do need a valid email address. Its only for getting your password. But after that there's no application or three day wait. The email thing should only take a few moments.
DartMUD has an easy to understand theme. Lots of helpfiles and tons of ingame books to read.
In my opinion, the player base is medium sized. But, that may be affected by when you log in. I log in in the middle of the night sometimes and still find a few players to RP with.
There's no pay for perks. I think there is a shop, or something though. But it sells shirts and cups.
Its basically a classless, level-less system. Each race has a preference to certain skill and every body has different talents. I've been told that learning to fight slows your magic learning down, though. But, I'm not sure if any other skills clash.
That's all I can think of. Hope you try it out. Everyone is helpful and can help you get started. If no one is in the center of tough, head south and through the gate (I think) to find the healer's hall. That's another place where people like to hangout. You can learn magic, find someone to show you around and a lot more.
Good luck on your search!