It depends on how you want to consider 'good', but I personally would love to see more children watch Steven Universe.
If your definition of 'good' means 'safe', without touching on anything potentially complex and generally trying to shelter a child from 'adult' topics then you likely won't like the show. However, if your definition of 'good' means teaching children to handle complex topics in a positive manner, and teach positive views and beliefs, then I can't recommend Steven Universe strongly enough.
The part that you may not like is that it starts out as a monster of the week style show, so there is definitely action and combat. You could rightfully complain about violence, though the nature of the Gem's body means that violence doesn't necessarily lead to real harm (since their outward body can be 'poofed' without causing any actual harm to the gem itself). The show does tackle the complexity of the violence though, with the main character hating to see anyone harmed and a strong message about learning to understand, communicate with, and potentially forgive your adversaries. I definitely would say I think it does a good job of showing the negatives of use of force and strives to idolize violence; despite combat definitely being a part of the story. Since your kids will eventually be watching shows with more violence anyways I figure it's better to start them with one that will discuss it realistically and honestly rather then just idolize it.
As to the positives, I feel it shows a huge number of good messages and tackles complex topics not usually depicted in kids shows.
The show is great about showing complex non-stereotypical characters. It breaks from standard gender/racial/sexual stereotypes and even addresses, by allegory, racial prejudice and how wrong it is. I don't think any kids show I've ever seen does a better job of encouraging people to accept others for who they are without encouraging or perpetuating, even unintentionally, any of the standard prejudices associated with race/sex/sexuality.
It also tackles many complex topics, many of which are rarely covered in kids shows. It covers topics such as feelings of inadequacy or failing to live up to a standard; regrets over past mistakes and difficulty of recovering from traumatic experiences; healthy, and what constitutes non-healthy, relationships and the need for communication, understanding, and consent within a relationship; accepting your idol may be flawed but still worthy of respect; and as I mentioned compassion & empathy for others, even those that may be working counter to your goals; along with many more complex but important topics. It does this in a subtle enough manner that a child likely won't realize the potential complexity of the subject matter, but still can learn and benefit from it.
I personally would love to see more kids watch the show for all the subtle, but complex, topics it manages to address and help children to deal with; and for how well it goes against standard stereotypes so common in children's shows. The one thing I would warn you about is that the real complex topics don't really start until near the end of the first season (it takes time to build up the world and characters before diving into them). So if you do decide to consider it don't give up on it you don't see the more complex discussions happening as much in the early episodes, they will come.
