Absolutely. The standard of design is dreadful beyond words, except perhaps bloody Partiko which I find simple, clean and intuitive.
My theories on this are that the super intellectual techie people would prefer to hire a coder than UI/UX specialist but if this is true, it has resulted in a load of , as you say, kiddies cartoon looking Interfaces which to be frank, are an embarrassment.
Function is important, but without form, no one's going to use it and I think 99% of Steem's issues are down to its complexity and amateurish after-thought design which gives out the wrong impression.

Steem Engine is awful. It looks like a school project. All the interfaces for the tribes just follow on the same design as Steem to compound the issue.

I wish someone would answer these questions for us as you may be right, perhaps its the code and Steem itself that doesn't allow for better UIs.