Until now, I probably agree with you that cryptos are some kind of gambling because it's so hard to predict any price or movement, that even real good analysts are wrong almost all of the time
With all the guessing, and predicting, and waiting on what will be the price this time to the next minute or hour, hodling is really somehow like gambling. In gambling, you don't really know if you will win or lose; and same here while hodling. I mean, one don't really know how much cryptos like bitcoin will cost. That explains all the price prediction threads here in the forum. However, they also have difference in the sense that, in gambling, it depends on either luck or strategy but in hodling, it needs more strategy and wise judgement on when to buy or sell.
Good judgement inside this industry will allow you to decide whether to take a risk holding your coin its similar like gambling with your fate, as there's no certainty in terms of market movements and exact time frame when the volatile market will hit up, understanding the sway to keep you from dealing as the same way as playing like gambling, but instead treating it as an investment form that will increase its value after some time of holding.