Pokémon GO is popular because it's a mobile game and it's a Pokémon game. I'd say the majority of
Pokémon GO players fall into one of three categories:
1. People who have never played a Pokémon game before, either because they've never owned a Nintendo system or because they do not play video games besides mobile gaming
2. People who played Pokémon back in the heyday but fell off the wagon at one point or another
3. Pokémon fans who are interested in anything Pokémon and are curious to see how far they can go with it
You have to remember that in most any type of game (and I mean anything, not just video games, but sports, board games, card games, any type of game), there will be a split between the beginners and the experienced. The two groups will look for totally different things in a game.
Pokémon GO was laser-focused to appeal to absolute beginners, people for whom Pokémon battling in a main series game might be intimidating or too complicated. In addition,
Pokémon GO is a nonfiction game (more or less): It has no story, the setting is wherever you're at, and it encourages participation in the real world. (You can see this reflected in other media too: Stories set in fantasy universes, like, well, fantasy and science fiction, are associated with geekiness, whereas stories set in plain old Earth with no fantastic elements are more associated with the mainstream.)
That is,
Pokémon GO's ultra-simplicity and premise might be off-putting to people who have been gaming for decades, but it is exactly what someone who might not play video games would likely want. It is the most beginner-friendly Pokémon game ever made.
Well we still don't know the details on Z-Moves other then its a Once time use attack. Like we don't even know if there is a difference in Z-Move Normal and Z-Move Snorlax.
Pulverizing Pancake is a Z-Move specific to Snorlax and is different from whatever the Normal-type Z-Move will be, just like how Stoked Sparksurfer, the one specific to Raichu, is different from Gigavolt Havoc.
So far, only the German name of the Normal-type Z-Move is known, which is "Hyper-Sprintangriff." That translates to "Hyper Sprint Attack," but I'm sure the English localization will come up with something catchier.