Card counting is still possible (albeit a bit harder) in the present day - the mathematics are the same. Most casinos use more decks and don't deal as deeply into the shoe, but it is still entirely possible to gain a statistical edge over the house, which is why casinos will still ban you from playing blackjack if you are playing with an advantage(counting, varying your best sizes greatly based on the count, sitting out and watching until the deck gets deeper, ect). They will never ban you from games like Roulette, where you there truly is no way to gain an advantage over the house regardless of what strategy you use.
