You forgot that we all used to be playing random civ in the past. Almost all games were all random pre DE. This was brutally changed to pick civ by the DE system. You have to know many players played this game for years an are used to this setting and wants to play with that settings. For that reason this is implemented. Players are used to certain settings and want to play with those settings. You seem to fully neglict this part of the equation, which for me is important.
For me the line is drawn at a good spot. If something needs to change, then it would even be give more priority to random civ. But that is also based on my personal preference. I can see why the devs decided to say it is pick civ if it is 50:50.