Sometimes I question myself if people posting these "a junior dev can build this product" haven't really worked with systems at scale and all of the myriad of issues that scale brings or if they are being the usual hyper-optimistic-dev that isn't considering much past the proof-of-concept point of a product.
Either way is quite baffling how common this kind of comment is, almost a decade reading Hacker News and it pops up constantly.
I remember this post from gregdoesit [1] as a good example of how much complexity is hidden under seemingly trivial interfaces. It's about Uber's supposedly bloated app, I believe that anyone who has worked at a scale where they had to support different national legal systems in their code would know that maintaining a large-scale product is nothing trivial.
Either way is quite baffling how common this kind of comment is, almost a decade reading Hacker News and it pops up constantly.