I really like playing ranked multiplayer pvp (played a lot of games like LoL Smite Hearthstone CSGO etc.), so I was very disappointed to go on the multiplayer page multiple times, and find that it's totally barren! In fact I only found 1 game once, with 1 person in it.
Multiplayer is not dead, just most games take hours/days to play from beginning to end so therefore it takes a commitment to play a game from beginning to end. I have a few people that get together on Sunday and Tuesday evenings and play. See forum post https://forums.galciv3.com/474942/page/1/#3619106
Aside from that the multiplayer portion of the game has been buggy to this point and is in need for additional love. Stardock has been very good fixing issues with their game and I suspect this will be taken care of in the near future. This may be another reason why the lobby is baron.
The last reason is some players are playing on different versions of the game. Many founders are playing on the opt-in beta 1.61 although open to everyone. Other players that haven't opted in are on 1.6.
Either way if you wish to join my MP group feel free to look me up on Steam (same name as here) and give me a shout tomorrow night. Thanks