Although this is not the game I prefer (on the contrary, I think it is one of the worst), and simply based on my perception, I also think that the most popular crypto casino game is slots. Maybe because of the sounds, the colours, the motion... or simply because of how easy it is to play (you literally press a button and wait for the outcome), it could easily be the most played game.
Yeah, I think you are right, basically, slot games are the easiest games to play in the world of gambling, I mean, it's just as you have said, press a button, and wait some seconds for the outcome of the game, there are no complexities, strategies to deal with when playing slot, you simply decide how much you wanna stake on each spin, and this also can be adjusted freely any time the player wants.
What about the auto-spin feature in slot games, that's also another very interesting feature of slot, using the auto-spin simply means, the player sets how much money they wish to stake on each spin, and then enter the number of times they want the auto-spin to run by it self, simply click go, and the player sits back and watch the system, algorithm do it's thing.
Slot games are the best games to play for fun with in gambling, but when it comes to making money, they are the ones where the player has the lowest chance of winning anything tangible.