Thing is, while these might be 'games' a lot of them need a lot of problem solving, and communication, and reading! My 4 yr old grandaughter can read fluently because she helps my oldest grandson read the text on the game he loves playing!
I believe schools put on a lot more pressure than we were dealt, this tires kids out a lot more, and they want to relax and play games, then at school, its part and parcel of playground life to talk about said games and discuss tactics, they aren't mindless the way some computer games used to be, they are role playing and complex, and I understand them a lot more now my eldest grandsons have explained them.
And to put your mind at rest, my four eldest grandchildren were exactly the same, coming home to play on their games, (although I would insist on a screen break every half an hour for their necks and eyes!) but now they are active, out at college and starting Uni, and wonderful kids.
This is how they enjoy themselves safely, and unless they are putting on masses of weight and seem depressed, I would leave well alone, but I do understand why you're worried, but I doubt its needed :-) x