There are definitely things that I have learned back then while playing RTS games:
- how to hold a team (clan) together and generally work as a team
- training a _lot_ and working hard on myself
- learning from my own failures (and analyzing my own replays), because in a 1vs1 situation it was always me that fucked up when I lost. I could never explain or rationalize that away.
- dealing with stressful situations and as ridiculous as it may sound, overcoming fears by using builds (changing strategies) I am not comfortable or confident with when all other plans failed.
But I wouldn't go as far as saying that RTS games make you a smarter person. It's always a question of determination and willingness to work hard, as it is in any other field where you choose to work in.
One factor in RTS games that might help facilitate determination is infrastructure.
In RTS games you have the infrastructure to compete with eachother on equal terms, which you simply can't do in many other fields you might be interested in as a kid because of barriers that prevent you from entering.