Think of it this way:
- You've purchased the ability to play 10-20 great games. Why would you then insist on playing only the least refined one of them all?
Pretty much by definition, mods improve something. Aside from the little "joke" mods that you don't hear about much (Like the Rock-Paper-Scissors mod), Somebody spent a lot of time making the game *better*.
Better in their opinion, yes. But if they like it, and a lot of other people do too, shouldn't you see if you like it?
Spoon's Fantasy Empires Mod is a good one to add to the list. It has been consistently popular for years, according to my server logs. You may or may not like the whole elves and dwarves thing, but the mod is very well done and looks great. In case you were wondering, yes indeed, the game plays out on the surface of a planet, with swamps and forests and deserts and blizzards and people running around with swords and spells.