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The problem isn't that there's 2 types of MMORPG, it's that MMO's separated and limited themselves into these divisions.
What happened to when you logged into a great big MMORPG world where you could choose what you wanted to do?
The world was enormous, and you could go anywhere, assuming you could survive the journey, beginning at level 1.
There were grocery list quests, if you wanted one.
There were walking and talking quests, if you wanted.
There was a story line set of quests, if you wanted.
If you want, you could just go grind.
There were monster pits of both similar and varying levels around the world. - For example, there may be pits with level 30 monsters in 6 different places in the world, one town offered a grocery list quest to kill them if you wanted, other places you could just hop in a pit and grind, hoping for some epic loot.
There were elite and group type monsters, that were hard to kill solo, but a group may farm efficiently and show good xp / loot for. There may also be a quest to farm them if you want it. There may be a story quest to work your way to the final boss of the dungeon, if you want.
Player housing? Sure why not, maybe, maybe not. Can destroy player houses? depends where you build. No rent in dangerous places, upkeep type tax rent to build in safe places like the city. - Players can still attack your house but guards will own them.
Don't want pvp or pk, don't want anyone to destroy your house? Sure go to the PvE server, not every server has to live by the same set of rules, that's why they're different planes of existence. Don't worry, you can still queue for an instances cross server battleground if you change your mind.
Instances? if you wan't, quests to go in the instances too. Play modes? why not? Group / solo instance? Sure why not just select what type of instance you want before entering.
Why do games and gamers want to categorize themself as one style and eliminate the other style? PvP / PvE, open world pvp or instanced only, sandbox or themepark.
The biggest problem I see with a themepark is that it is hard to make a sandbox out of it. While it's really easy to build a themepark inside a sandbox. Why can't companies offer a themepark route through their sandbox? Offer a few different playstyles to partake of depending on which server you join?
People act like it's impossible to please everyone, I don't agree. The limitations placed within the walls of the game are what displeases people, not what it offers.