Am I the only one with issues with Sing Street?

Rating: 2/10 (10 June 2016)

I've seen some comparisons with The Commitments for Sing Street - an Irish musical so I understand the comparisons. However, even though The Commitments had ten main characters all of them have screen time. Unlike Sing Street- only 2 members of the band are given any screen time.
The other 3 members of the band are glossed over. The black member of the band is ONLY asked to join the band because of his skin colour. The other 2 brothers could have provided so much more.
The main female character in the movie - I only registered her name in the second half of the film - but the songs are catchy so it's fine, right??
So many underused actors/characters. It's clear the director has a close bond with his brother. It's shown between the two brothers in the movie and hat the film is dedicated to brothers - then what's the point of the sister in Sing Street? What was her name again?
Racist and sexist. And a waste of talent.
But catchy tunes, right?