I don't mind Civ6 for solo play, but for multiplayer it's a no-go for me. Turn lengths get to be so goddamn long because everyone is worrying about all the mini-game mechanics.

Civ5 is what is used for multiplayer in my group. The mechanics are simpler and there are far fewer decisions to make as you get into the end game.

If I was going to make a 4x, I would make multiplayer the #1 priority and I would focus on the turn length. There are plenty of 4x titles out there if you and a buddy want to burn an entire afternoon playing through one turn each.