As plenty of reviews have already stressed out, this is very much like an other idol show. It is not necessarily a bad thing. There are plenty of shows that became successful following a particular format, and those achievements should not be diminishes. Look at Kuroko no Basket. It just happens that Bang Dream falls in that specific genre. So, onto the review.
The story is very basic. A high school girl, Toyama Kasumi, looking for inspiration, follows a trail of star stickers to a pawn shop, where she finds a red star shaped guitar. She decides she wants to learn how to play the instrument and find people to put a band together. Everything works out in a way or the other. She finds the right people to play in the band and they are able to perform on a live stage. With some complications along the way, but you get the point.
Through out the story, the main characters go through some major character development, making them a little bit fleshed out, and a little less one dimensional. At the beginning of the story they downright look like stereotypical anime characters, but to the end, you can see their personalities shine with all their flaws and imperfections, making them all extremely relatable and likeable. Even the ones that you are not completely fond of.
The animation is not horrible, but they could have been able to do better. The CGI aspect is really cool looking, but it just doesn't save some of the more atrocious looking parts of the animation.
What really stands out from this show, in my opinion, is the music. This is no Nana or K-On, but the music is still pretty darn good. Rock songs have always been my favourite thou, so I might be a little biased while going into this, but you cannot tell me that Time Lapse doesn't friggin pump you up. It makes you wanna do a massive workout, and run around doing stuff. It is very classical rock, with tones of pop and and musical theatre, but you kinda get the gist. If you like idol anime music, you will probably like this kind of music. Poppin'Party is pretty standard though when it comes to Bang Dream music.
There isn't just one type of genre. If you go into the game, there is a whole variety of songs to listen to from five different bands with specific styles and songs. That is what makes this franchise so much fun. Putting different bands together to showcase the genres out there (ranging from musical-theatre to gothic), with relatable characters and fun stories, is something that very few have done.
To be honest, the reason why I am giving this review 8/10 is because I play the game, and I can see the characters, the story and the music develop in such a way that you don't really see in the anime. If you are just gonna watch the anime you might be a little disappointed, but if you go into the game, you can just see why it is so compelling and fun. My favourite band isn't even Poppin'Party (Toyama Kasumi's band), yet they are still lots of fun to listen to.
Lastly, Bang Dream in reality is not about Poppin'Party. Bang Dream is Poppin'Party, Afterglow, Rosalia, Hello Happy World and Pastel Palettes. Bang Dream is about finding your own musical preference and style, while obviously finding entertainment in cute girls and pretty cards.