I wasn't a Thundercats guy. I was He-man all the way and like TF/GoBots or later the console wars, I felt I had to pick a side.
But if my kid likes this and we can watch together? That's only a bad thing if you're an asshole.
Nobody's saying that you & your child enjoying a piece of media is bad, but art is subjective. We can still find qualms with the piece of media itself. And there are many qualms to be had if you're not assessing from the perspective of a child or their parent supporting said child.
Truth of the matter is that Cartoon Network is bleeding child viewers, & only adults were clamoring for more Thundercats. The art style is designed with what is cheapest to make while appealing to children, but if they don't suddenly care about Thundercats, this show's doomed. The criticisms this show is receiving should be taken to heart; it's being bashed everywhere.
EDIT: Added for Relevance