Daniel Tiger is so much more difficult to watch as an adult, but I have to give it credit for its potty training episode: that was a
huge help when trying to potty train our 2.5-year-old. So I definitely agree that a targeted application of Daniel Tiger can really help, and also easier to digest for a pre-schooler.
However, I do think that having complex messages that aren't easy to understand is probably important for young children. "The world is a complicated place" is a lesson I wish even more adults understood. And I've learned that children may show no comprehension of something the first few times they hear it, but it's in there, making connections, shaping the brain as it grows. I can't tell you how many times I've told my daughter something I thought went way over her head (and did, at first), but randomly came out again months later. So by all means go for the simple Daniel Tiger message when it helps them through a problem they're having. But don't underestimate their capacity for deeply integrating ideas from everything they see and hear -- and I love Bluey for being by far the best young kids' show for them to integrate into their brains.