Also I will say Classic has toyed with the idea of procedural dungeons. Dungeons that are randomized but filled with predefined content and rooms. Every time you played the layout was different, rooms would be different, filled with different baddies. You beat a floor, go down further and get a larger floor, with tougher monsters. Do this until you die.
That's the dream for Classic, at least my dream for Classics dungeons. I think something like that would put Classic on par with other servers to a degree. And no I'm not spewing stuff out of my ass.
If Classic had a system like this in place we could release "new dungeons." Dungeons that had a new theme, say, an ice dungeon. Ice baddies and such. Most baddies would just be recycled from a base, for example what was a rat in the other dungeon would be an ice rat in this one. But players wouldn't care. We could even give it ice-themed abilities(current rat on Classic has a rare version that explodes when touched) that could spice it up and make this dungeon different than the other dungeon. A system like that is a system that is built for recycling, and what could make developing on Classic somewhat easier.
But there is a huge upfront development cost to this, and cost aside it's nearly impossible. Procedural generation would put a strain on the server that it can't handle. It would need to be offset to another server. Then there are other problems, such as multiplayer vs single player. Multiplayer means dumbed down gameplay. Because a dungeon filled with just mobs in a Zelda-like experience means dying and getting kicked out due to lag would be infuriating and unfair. And dumb mobs are just boring imo, when the entire focus of the dungeon is fighting them. Hence emphasis on pathfinding and creating smarter enemies that would be fun to fight. But pathfinding + serverside(because of multiplayer) = a big nono. There were too many obstacles to overcome, and it would need to go through channels that wouldn't get it done.
But, if Classic had this then yes, I think we could compare the development effort to Classic to that of MMO's. It would provide Classic with its base for a core gameplay mechanic that builds off of recycled content.