Keep in mind a good portion of the multiplayer was paid DLC before. Now everybody has the DLC for free. In fact, those three maps you listed are all DLC maps. And the DLC maps are indeed phenomenal. Also, some of the monsters, guns, armor, etc, were paid DLC as well.
So the multiplayer is definitely more varied and full-featured now. I'd say the main reason people criticize the multiplayer is because of loadouts. Since all the weapons are available via loadout (except the one power weapon on each map), that means the weapons have to be balanced across the board instead of something like a Rocket Launcher being and feeling more powerful. Also, the use of loadouts means less focus on controlling weapon spawn points around the map. Obviously there's still a good amount of map control involved since there's still various pickups around the map with no regenerating health, but compared to a typical Arena Shooter there's less of a focus there. There's also less movement control in the air compared to typical Arena Shooters.
Basically, the DOOM multiplayer is a console-friendly Arena Shooter, for good or ill. Personally, as a console gamer I enjoy the multiplayer quite a bit.
No idea, but they usually do one whenever they make a notable update to the multiplayer. And who knows when or if they'll update it again.
