No, "saccharine rainbow powers solve everything!" Isn't "deep". Not even for a show intended for children.
Want a show that really is?
Its intended age range is 8 and up. (Hint, that's most of the same age range for MLP, which is 6 to 12 (and bronies).)
I saw it when I was 7. My parents had already explained death to me, and the cold war was still going on. It did not leave me with emotional baggage, and I liked it, much like this reviewer liked it. It depicts "serious shit happens! Only hard work and bravery really fixes it."
It prepares older kids for the not so nice things in the world around them as adults, and helps them be more than 2 dimensional emotional fountains when the saccharine landscapes they were sheltered in are violently ripped away.
I wouldn't show it to 6 year olds, but 8 year olds should be able to handle it, if their parents haven't tried to unnaturally extend their childhoods with a diet of saccharine to stunt their mental and emotional growth. Thankfully, my parents fed me a more healthy diet of media that featured consequences and resolutions that had real meat in them.
MLP:FIM is not "deep". No, Not even for a kids show. HR Puffinstuff had deeper meanings hidden in it, and it was made for 3 year olds.
Children need to learn that "saying sorry" and "let's be friends" doesn't absolve dickery, and it doesn't fix a wounded heart, or a scarred mind. It helps, and is the first step, but that road is a long and hard one. Friendship isn't really magic.
It isn't about being noir, or gloomy, or broody about things. That's equally unhealthy. It's about accepting consequences, and learning that often times the best ways to avoid those consequences, BECAUSE they are hard to resolve, is to just not do those things to begin with. (And when you have to, accept those consequences gracefully and with maturity.)
If the people hooked on the saccharine in MLP were absorbing THOSE lessons instead of cancer causing sugar substitutes, they wouldn't be as callous about their candor with other people and other people's interests, and react so violently and negatively when people demand they stop. (No, putting pinkiepie in places she does not belong is NOT 'cute', and IS an offensive gesture. People getting mad about it and telling you to stop is the consequence, acting like a petulant child and throwing a fit and resorting to creating lynch mobs and retaliatory strikes on communities outside the fandom is aggression, and people hating you and your lynching pals for it is the consequence. Saying "I'm sorry!" In a saccharine sweet voice, then going off and doing it right away again like nothing happened is NOT resolution.
Again, you would have learned this, if you watched things with *real* substance.
MLP is not such a food item.