Novice Question about models: "2 Variables + 1 Filter Models"

I was listening to a well established discretionary trader who uses models to basically come up with trade ideas and test them but executes the models herself. She mentions that all of her models are 2 variables + 1 filter. # What are your opinions on setting up models this way? To me it seems too simple but I don't know anything about making models and I know models are a vital aspect of what algo traders do.