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.
You actually mean games that doesn't need strategy and mental exercise to execute results? If that's what you mean, then yes. Playing slot, Plinko, dice and non strategic based games are prone to cause mental dullness in any individual that constantly participate in this game and never try other strategic based games.
The brain needs it to be functional, troubleshooting to be able to expand, and these games do not give it such function, just making players been dummy hitting on the stake button without knowing what would happen next, just mere luck.
So dummy to me.