I think the main thing that killed RuneScape for me was the natural removal of being able to train one skill through another.
Like this for example:
Mine some iron, smith it, smelt it, sell it for a decent amount of money
Use this money to buy logs and flax, and nature runes
Make magic longbows and then alc them to get money back for training another skill
But the trouble is because of natural changes in the cost of items (supply and demand), it is now no longer feasible. The cost of the logs, flax, and nature runes come out to a LOT more than the money made from alcing them. As such, there is no point in training magic this way.
I had a good system going, left for a year, and suddenly the whole world had changed ~