Simple GamePlay mod that SLIGHTLY REDUCES city spam. New cities now need to be 5 hexes apart instead of the default of 4.
Note: This is a recreation of the previous resource/mod noted by the below link. As I was unable to change the original post's type (from 'no files' to 'with files') and then upload files (hence this recreation).
Mod also available via Steam Workshop:
Cities at least 5 hexes away 1.0
New cities at least 5 hexes apart (4 between)