I think you underestimate how much time is spent on art and sound and other non-gameplay related work. For example take a look at my civ concept for Hungary
I spent hours and hours on this. This time was mostly spent on reading and research to try and get a historical basis around which I could develop a cohesive civ identity, including landmarks. And I didn’t even research things like the languages and architecture in different ages. So if I were to see Hungary released as a bastardized version of the French (imagine having Magyars without Horse Archers), it would basically be like a huge slap in the face.
I can understand your point to some degree, however. My concept of Hungary basically used Pit mines almost identically to how they are used with Mali. So I would be ok with these two civs having a similar bonus. Just like Rus and China both have faster firing bombards. But pretty much everything else about Mali would be completely inapplicable to Hungary. So the concept of ‘clone civs’ as you describe them would not really speed anything up and would alienate more people by presenting a poor identity of the civs.