I still think 90% of what made UO unique is the fact there was no Google or central repository of expert knowledge. Yes, UOStratics existed, but it wasn't perfect. A lot of the fun was in the fact basically nobody knew the BEST way to play, and therefore everyone was just doing whatever they thought was fun.
If someone create a new MMORPG in which rules changes a little every day or several days in unpredictable manner then no one will be knowing the BEST way to play or at least harder to find the BEST way. But maybe there will be no balance.