The updates aren't coming out too often, despite the number of bugs plaguing the server.
The GMs aren't all on the same page when it comes to bans, warnings, etc..
The scamming runs rampant because the staff are unwilling to put in time to prevent it.
The events aren't run at times when most people can enjoy them. I'm an average person who works 50 hours/week, and I've yet to see one event since I joined months ago.
The DShop prices are pretty steep, considering you can only get coins through donating.
The Aloken class is overpowered. 75% physical resistance for 15 seconds? ~1,300 defense from a +9 Guard? Great job.
The status icons for buffs are screwed up pretty bad.
The rewards in DF are inconsistent.
The drops are also inconsistent. Only the Doom map drops from mobs, for instance.
The descriptions of DFs are incorrect. It's a little confusing trying to find the DF you're supposed to be in when all the levels have been changed.
The visual effects for Summoner sacras can cause lag, even on good computers, because the effects are messed up. That arrow is for Point Target, fyi.
How many Dekaron private servers are left? How many have actually been able to prevent most forms of "hacking"? Answer those two questions and you'll know why Evolution is popular.