The stories I heard made it seem like a wonderland stuffed with gummis but when I got there there really wasn't that many, 1 per floor mostly...
I haven't heard such stories, I don't know where you got that (unless you have Sky, in which case, that makes sense). I expected Water Pokémon at the resort, but it was mostly non-Water Pokémon. When I think of "Gummis galore!" I think of Craggy Coast, as that was where the game said Blue Gummis were abundant when Manaphy was starving.
It's also the same way with Aegis Cave. It was supposed to be a neat cave, but it got frustrating really fast going through three short rooms and not finding all of the stones needed to proceed, and getting stuck in a loop until you found them.
One gummi per floor on average is still better then pretty much any other dungeon.