The American Association of Pediatricians recommend that children under 2 years old have zero screen time, and that children over 2 have only have 1 or 2 hours per day of quality screen time.
Quality is partly subjective. Some things you may want to look out for are:
1) Positive behaviour. Children sometimes copy poor behaviour. There is lots of anecdote about children copying poor behaviour.
2) Diversity and equality. It's good to show confidant women, caring men, and so on. Characters with disabilities give you the chance to talk about those with your child.
3) Age appropriate. Sometimes you want your child to be learning things and to be challenged by what they watch. Sometimes you just want them to relax and watch something fun.
4) Production Values. It's important for children to be able to hear what the characters are saying.
5) You might want to avoid advertising.
There is a lot of programming aimed at children, and most of it is terrible.