I've read some reviews and I realized that whether you'll enjoy this anime or not will depend on your tastes.
For me, I enjoy anime that are nice to look at. Whether it be through the character animation, like in One Punch Man, or through its overall art and world style. I also appreciate a good story and lovely characters, but first and foremost I look for beauty in animation and art. It's a bonus if I get the good story and characters.
Granblue Fantasy is absolutely beautiful to watch. Visually. The scenes are as if they're straight out of a painting, and the characters and creatures never move awkwardly, all throughout the anime. You know what I'm talking about: anime that are only animated well for the first few episodes and for the rest of the season are lifeless caricatures that can talk (Masamune-kun no Revenge), or are never animated all that well in the first place (Getsuyoubi no Tawawa, but don't get me wrong, I enjoyed it, although for reasons I will not state here).
Its story isn't really a novel one. Its characters really aren't fleshed out, but there isn't any need for them to be for me to enjoy this anime. The character chemistry isn't bad, but again it's pretty basic (see what I did there?)
In conclusion, if you're like me, and your idea of a good time is watching anime that are well-done visually, give Granblue Fantasy a shot. I recommend watching it on a large screen.
But if you're looking for anime that'll tickle your funny bone, or make you fall in love with the characters, or get your mind up and running, or give you a completely new sense of perspective---you might wanna pass on Granblue Fantasy.