Nash equilibrium certainly applies to No limit hold 'em. It's a zero-sum game with finite choices over finite time. Could you explain why you think otherwise? Are you just saying it's practically impossible to calculate?
It's theoretically possible to find Nash equilibrium over all possible strategies but that's not winning strategy. You just lose as little as possible. You lose against most/all strategies.
Take for example Kuhn poker (https://en.wikipedia.org/wiki/Kuhn_poker). It's very simple but first player has several optimal strategies.