This is not true. Besides continuous shuffler machines, most casinos have 6 or 8 deck games that have plenty of 'penetration' (card counter term for depth into the deck that the cut card is placed) to offer an edge if you properly card count. There's also a big game to be played where rubes think they can card count and instead lose tons of money attempting to do so.

The problem with card counting generally is that the casino has infinite money and never runs out, thereby they can sustain large expected value swings... whereas you need an enormous bankroll to handle those swings, assuming they don't throw you out before that happens.