Really, what are the standards for an animated film to be considered "good?"
Despite some bad reviews here and here, I actually saw Sing and I thought it was a good movie. I liked it about as much as I liked Zootopia, so if you didn't like that, well, I don't know what to say. This film does not avoid sadness and it does not insult the intelligence of children. Yes, it is fun and upbeat and has some slapstick to it, but it does not avoid telling you that show business sucks most of the time. If I had to point to one thing that allows the film to succeed it is that it arrives without assuming you haven't already seen what goes on behind the scenes at talent shows. It assumes you know that there's going to be conflict and drama.
Sing owes a lot to the animation esthetic at Illumination (the Minion movie, whatever else) and you can easily be dazzled by what you see. It's a rich, diverse tapestry and, a few stereotypes aside, it works very well on the screen. So, relax. You're not going to be ripped off.
Now, having said that, the plot is a mile wide and an inch deep. You know that down on his luck Buster Moon is going to take a fall and climb right back up. You know how the movie will end when the whole thing kicks off, but it's the journey that works. You will not mind the episodic format and you will want to see more of certain characters. There's so much happening in this film that the plot will not bother you at all because you're already seeing all the different ways these characters are looking for some sort of validation.
Somehow, they made Matthew McConaughey lose every bit of Texas from his voice. Somehow, they managed to make Scarlett Johansson not sound exactly like herself but like a teenaged girl instead. Reese Witherspoon and Seth McFarlane are part of a broadly drawn cast of weirdos and misfits and it all somehow works. McFarlane in particular fits into the whole thing like a completely square peg being dropped through the other side of a round hole. He's not even really part of the team, he just kind of floats through this thing like comic relief. And, as always, you're going to wonder why Jennifer Hudson doesn't already have her own damned franchise already.
There's an especially weird diversion towards the end of the second act that involves washing cars and acting loopy and it's absolutely worth the price of admission. The rest I'm not giving away.