Is scrabble for smart people?

It must be. I never won a game in my life.

I don't think you have to be above average intelligence to play but you need a wide reading vocabulary (most people know more words to read than they use when speaking).  Like all games there's a learning curve, some people are too impatient about that.  I was fine learning scrabble, but yatzee was too much for me, lol!  Play scrabble with players similar to yourself and it all evens out.  It's no fun when one just one person is visibly struggling because they don't know enough words and it's no fun when just one player is light years ahead of everyone else iyswim.  If scrabble seems too daunting try Boggle (the one with the cubes you shake).