Yeah, it's hard to argue with "Diablo-gameplay, but as an FPS" then add
post-holocaust and you've got a winning combo.
Then I think there was some fairly complex stuff happening, probably largely because this was a first-time effort of a mainly ex-Blizzard team, working for a publisher which was not Blizzard, and in fact was Namco, EA, and another Korean company. They likely faced weird pressures from each, as well as foundering on the non-Blizzard work environment. Plus, for its time, this is considered
greed:
There were two types of multiplayer accounts: free and subscription accounts. Subscribers had access to ongoing content updates.
The US subscription plan cost $9.95 (USD) a month and an offer to pay a one-time fee of $149.99 for a lifetime subscription was available for up to 100,000 people who pre-ordered the game and ended on January 31, 2008.[12] The UK subscription is £6.99 and EU subscription is €9.99.[13]
Additionally, subscribers would have access to a Hardcore mode, special PvP arenas and a PvP ladder, the ability to bypass server queues, a shared storage space with room for 40 items instead of 20, the ability to create guilds, the ability to achieve officer status in guilds, and 24-hour customer support.[14] Subscribers and non-subscribers were able to interact in all ways in the game. Non-subscribers could join guilds, but not create them.[15] The level cap is set to 50 and up to 24 character slots are available for all players.[16]
There's so much that's locked off to the non-subscribers, and this wasn't really marketed as an MMO, at the time the only genre for which people could rationalize a monthly fee.