It's said about brain that, "use it or lose it" — now, question being, do you think if person plays brainless gambling games such as slots, dice for major part of his/her daily routine, will it make him/her dull?
Edit: "brainless" as in playing gambling games that does not require using brain, I thought it was clear especially given examples.
Who told you that you’re not using your brain when you’re playing slots? It might not be a complex usage but surely your brain is computing things and this will keep your brain a little active. Besides, you’re not spending the whole day on your screen gambling - you’d still leave to do other activities to help your brain improve its function.
You don’t have to complicate things before considering them learning or helpful to the brain, fun things can also help your brain too.