Can't Build Any Leaders

[GAGA Extrem]

It looks like you are playing with "historical" setting for kings and leader. With this setting you cannot offer any marriages and you cannot recruit any leaders by yourself.
And since this mode is more or less experimental, there won't be many leaders around.

PS: You also need a diplomat to recruite a leader.

 

[GAGA Extrem]

Ugh, you're right. Enabling that option was such a dumb idea. What do I do? Just start over?

Unless you can change the settings in your save file (which I doubt), yes.