Multiplayer of this game is completely dead - so not worth the buy due to that.
If you want SP or play the Aliens mode with friends then you need DLC-s otherwise you can only buy 1 map.

There are probably small communities that kep hosting events in MP etc.. But other then that this game is long forgotten

Just bought to play Extinction as it is amazing and nostalgic for me. Have been playing since pre order on the PS4. Dont know about the rest of the game.