It is indeed gambling but compared to gambling, time is your enemy, you have no idea when are the coins that you are hodling will reach their all-time high, and every day you have to follow the market and how your portfolios react, one thing that you need to study or to plan is when is the right to sell your coin.
Its completely different, the only thing that would make it a bit looking similar is the fact they both involve risk but aside that, they are not the same at all.
Gambling is purely a game of luck and full of uncertainty while crypto holding is just a mini risky investment and anything investment is and will always be safer compared to gambling. The only reason some people compare gambling and crypto holding is because they are both unpredictable but still we all know that money I kept in bitcoin will never get exhausted no matter how down the market might go, it could go down and the next minute bull run but in gambling, once the money is gone, it can never be recovered.