Why haven't we made a very high-level programming language which accepts code that anyone without programming knowledge can understand?

Because we need something called a compiler to translate the code we write into instructions which are things the CPU understands and executes and the more high-level the language becomes the harder and more complex making the compiler gets that’s why for languages like C# and Java you’ll find that they use an interpreter which essentially compiles the code you write in run time but that process itself is time consuming relative to other low level languages like C or C++ and when speed and efficiency is the end goal for most software that gets built then the prospect of having a language that anyone can understand and write is ridiculed if not ignored.