Of Course It Is...
It is ABSOLUTELY GAMBLING...
You are GAMBLING that your combination of SKILL AND LUCK is good enough to profit vs. your buy-in. Bigger Picture, over many games, still the same concept, just over more time.
Because of the randomness of cards, and randomness of player decisions, there are no guarantees in poker. The best player does not always, perhaps even rarely, win. You are gambling, no matter your skill level.
Obviously, the more skill you have, the less luck you require to win, and therein lies an edge, but still a gamble. Perhaps if we could all play 5 Million hands against each other (and I would argue this is a small sample size) at equal stakes, then maybe we could say those that won big were not really gambling, they were just better than the rest of us.
Best of Luck at The Tables All,
CheezeWiz