Client side development, for the most part, has long been treated as a second class citizen to server side development. Writing code on the server side is seen as more complex and requiring of more foundational knowledge than client side development. Its true that there are a bazillion potential solutions to back end architecture, and a developer worth their salt should have comfort with a number of them. Not every back end developer is alike, and I have tremendous respect for those that are skilled at it and are, personality-wise, an asset to any team. Being slightly lower on the stack, albeit still fairly high up, a deeper knowledge of computer science principles will undoubtedly be useful, which no doubt contributes to the air of complexity.