The biggest innovation of The Settlers of Catan may not have been its gameplay but instead its production. It reduced instructions that were previously available only in the rulebook into icons and glyphs that appeared on hexes, cards, and player aids.
This major benefit of this innovation was usability. As the eurogame industry replicated this concept, its games became a lot more playable: players didn’t have to remember as many rules; instead they were elegantly printed on the components (or sometimes integrated with them).
A secondary benefit of this innovation was internationalization. A single printing could be made for a game (or for some of its components) and then sold into multiple countries. However, this should at best be considered a useful side-effect. Icon design that concentrates on internationalization instead of usability can actually damage the players ability to play that game, thanks to icons that make a game harder to play because they replace elements that should have been text. If internationalization is a requirement and a game really doesn’t require text, great, but if it does, then either the game needs to be changed or the text needs to be included.
However, creating icons for usability (and perhaps internationalization) isn’t as simple as just scribbling little pictures on cards. It requires design that is as careful and precise as the design of the game itself.